Popular Science Monthly 1925-04: Vol 106 Iss 4

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opular Science RADIO SECTION PAGE 74 How you can replace “B’’ batteries with alternating current. An easy way to add a radio-frequency amplifier to your set. azing plane its own parachute See page 30 25 CENTS

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5. hestra Naster ‘al, an ve-old opera —near! Super- “nce — ounds, POPULAR SCIENCE MONTHLY SUMNER N. BLOSSOM, Editor April, 1925 The Magic Stuff that Saved Nome How, in the Blood of Horses, Are Produced Invisible Conquerors of Human Disease By Edward Mott Woolley NEW Epic of the North, greater by far than any from the master pens that have celebrated the Arctic, was written recently when seven relays of intrepid mushers, lashing their dog teams to unprecedented efforts, sped over the trackless Alaskan trails to carry life-saving antitoxin to the city of Nome, stricken by an epidemic of diphtheria, the famous “‘black death” of the North. Fighting withering cold, fierce gales, and roaring blizzards, these Spartans of the snows urged on their fleet huskies to accom- plish the 660-mile journey from Nenana to Nome in the record- breaking time of 12714 hours— approximately 514 days—faster by far than dog sled ever had traveled before, even in the “derbies” —races for generous prizes—in which the best Alaskan dog teams contest each year. Never did the purses and honors of those derbies prove such reason for pressing on to the very limits of human endur- ance as did the call of suffering humanity that seemed to ring in the ears of the drivers as they struggled over the snows. Twenty-seven persons lay sick of the dread dis- ease when Gunnar Kasson and his 18 dogs pushed wearily into the settle- ment with the precious 20-pound package con- taining 300,000 units of the life-saving serum. Twenty-eight others had developed what appeared to be symp- toms of the scourge While Kasson, and Leonard Seppala, most famous of all Alaskan sled drivers, and Tom Green, and Shannon, and Nicolai and the others were carrying the needed serum over the snowswept trails. A frightful list of patients, this, in a community with a population of between only 600 and 800 souls. Compute the same proportion of dis- ease cases in a city of a million, and you will appreciate how critical the situation was. The eyes of the whole world have been turned toward the little settlement on the fringe of the Arctic Circle ever since the telegraph first told of the .» grim drama that was being played near the top of the world. Aill honor has been paid to the courageous drivers, who, with striking mod- esty, said that their feat was ‘‘all in the day’s work” and insisted upon pass- ing credit along to their dogs; also to Dr. Curtis Welch, ! # F Heroes in the Race with Death Leonard Seppala, champion musher of Alaska, with two of his famous lead dogs. 245 miles of trackless snow in the longest of seven dog-sled relays that carried 300,000 precious units of diphtheria antitoxin to plague-stricken Nome. In the face of a raging blizzard they sped over All Alaska speed records were broken Germs to Fight Germs Inspecting the growth of bacteria in laboratory cultures. The killed bacteria, injected into the blood of animals, arouse the life cells to produce the disease-resisting antibodies that are contained in the antitoxin serums of the U. S. Public Health Association, who, with the assistance of a single nurse, battled ceaselessly with the hosts of death before the antitoxin arrived. But there are other men—other ani- mals, too—deserving of credit for the parts they played in that thrilling episode. They did not face the rigors of the Alaskan winter, nor dare death under circumstances so dramatic that the atten- tion of the world was focused on them. Yet in their own way they served, and served well, for it was they who produced the magical stuff—the antitoxin—without which the heroie efforts of the Alaskan sled drivers would have been in vain. [t IS a fascinating story, this tale of the efforts of science to end the ravages of diphtheria, pneumonia, ty- phoid fever, spinal meningitis, erysipelas, lockjaw and the other deadly maladies of humankind through the production of what scientists call ‘‘ bacteria antibodies,” or “‘immune serums,”’ which are Nature’s weapons against the germs of disease. All around us continually lurk whole armies of invisible enemies of human life, inhabiting that vast and mysterious un- derworld we call disease, and watching always for a chance to gain ingress to our bodies. We speak of these microscopical despoilers as bacteria, which by the use of a little imaginative license we may endow with attributes of crafty intelligence, ever 27

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Lo el 4u eager for the deadly contact with human kind that will give them entrance to the blood stream through mucous mem- branes, pores, or skin abrasions, or, with greater cunning, by way of the hair follicles. ACTERIA, indeed, would speedily destroy us and wipe out human and animal life except for a mystifying force within ourselves known as “natural im- munity.” ‘This is a wonderfully fascinat- ing subject, about which little was known until comparatively recent times. But when biologists began to unlock the secrets of natural immunity they not only revealed a new and unsuspected world, but discovered strange possibilities for the treatment of disease. They found that natural immunity was a tangible force, lying largely in the POPULAR SCIENCE MONTHLY The Rescue Trail at Nome From Anchorage the 20-pound pack- age of life-giving serum was carried by rail 300 miles to Nenana. The re- maining 660 miles to Nome were accomplished by dog teams in 5!4 days eae ee ¢ MN eon ctnae cstiy | ‘ ability of the boay cells to produce antitoxins and other substances with which to repel the attacking enemy, bacteria. These discoveries were pivoted on studies of the body cells. Without going far into the realms of fancy, we can say that every human cell is virtually an animal in itself, and that the human being is made up of vast colonies of these cell animals. Some of them are working to build and maintain the body. Others, known as the “‘ white cells’”’ or “‘leucocytes,”’ or sometimes “‘ phagocytes,” are wandering cells, with power to elon- gate and propel themselves from one point of the body to another, passing through the tissues with a peculiarly penetrating power. The phagocytes are among the chief fighters of disease germs, which they devour. With a powerful microscope they can be seen in motion, carrying fragments of bacteria. To accomplish the overthrow of the bacteria and reduce them to a form in which they can be digested by the pha- gocytes, the body cells produce and throw off into the blood a mysterious something, possibly chemical substances, \ Magic Weapon Against Plague Tis little bottle contains 10,000 units of di; theria antitoxins, sufficient for one treat- mdépt. Thirty times this amount was carried in the§ dramatic dash over the snow to Nome, whe 27 persons lay sick of the dread disease whic scientists call “antibodies.” These antibedies never have been identified as visible entities. Just what they are re- mains to be discovered; but although they never have been seen, their presence or absence can be ascertained positively. Just what antibodies will do is known to a certainty. Every different form of dis- ease, moreover, is combated by its par- ticular antibody in the blood. Unsung Hero Injecting diph- theria toxin into one of the won- derful horses that produce’ the life- saving antitoxin in their blood SERUM one TO NENANA. * BY RAIL Every person in normal health has enough antibodies in his system to destroy a reasonable quantity of almost any sort of bacteria. This is natural immunity. When an unusv- ally large quantity or especially viru- lent type of bacteria gains access, or when the subject is weakened or even temporarily exhausted, the natural immunity is overcome and disease gets the mastery. S° SCIENCE, as represented in the fields of medicine, bacteriol- ogy, and biology, has discovered by extraordinary experiments how to produce antibodies artificially in the blood of horses or other animals, and how to separate and purify the serum containing the antibodies after it is drawn from the blood stream of the animals, making it safe for injection into the blood of persons suffering from infectious diseases. At Glenoben, Pa., not far from Phila- delphia, I saw recently a herd of wonder ful horses, which are devoting their lives to growing in their blood these mysteri ously invisible, yet tremendously real antibodies. These horses haul no drays and drag no plows, but live in equine luxury, protected by every sanitary device, fed on the choicest of stable pro vender, groomed and petted and exercised as the aristocratic horse should be; all because their blood streams are the garden soil of science. Without suffering or inconvenience they produce, through nature’s own miracle, the very substances recor: carrie West result rout. few than T? acros infrec wagir it is under escap It j Milto H.K. to wh mater forces lines, deals ally {j prote

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th has item to tity of This is unusu- ly viru- CESS, OF or even natural disease nted in acteriol- ered by how to y in the als, and 1e Serum ter it is n of the injection suffering n Phila- wonder- 1eir lives mysterl- sly real no drays 1 equine sanitary able pro- exerci be; all are the suffering through ibstances POPULAR SCIENCE MONTHLY 29 selves, killed; while a serum is obtained from the blood of horses or other animals containing the antibodies pro- : duced artificially. It was found : . that killed bacteria, when injected : om aa into man or animals, would arouse ak, the antagonism of the body cells, A much as the live bacteria would do, and that the cells would pro- ceed to generate antibodies. Going a step further, the re- | is a solution containing the germs them- Leonard prunt in ala and his Siberian huskies which bore the z ay z ee most dramatic race against death. great discovery serobacterins, a search scientist made another Togo, Seppala’s famous lead dog, was lost on the journey product containing both antibo- that we ourselves produce in our own blood, in normal health, to crush or poison invading microbes of death. These horses receive at first minute hypodermic injections of killed bacterial cultures or their poisons. This imme- diately arouses the animal cells to produce antibodies. Gradually the doses are in- creased, and at last the horses are pain- lessly bled. The serum is refined, tested for purity, safety and activity, and then bottled. T WAS these very horses that supplied I most of the antitoxin rushed over the snows to relieve disease-infested Nome. It was these very horses that, only a few months earlier, supplied the serum that checked the outbreak on the Pacific Coast of the now rare pneumonic plague, the black death that killed millions of people in the fourteenth century. In the foreign section of Los Angeles a woman died from a strange and galloping disease, and of those who attended her funeral nearly all met with a similar fate. Los Angeles turned to medical science for the identity of the dread invading germs, and the answer was quick and positive. Rare though this diabolical disease has become in modern times, the biological laboratory in Philadelphia, which I have mentioned previously, had an _ anti- plague serum actually in stock, awaiting the possible call of emergency. Within an hour after the transcontinental tele- phone brought word to the laboratory of Los Angeles’ need, 500 doses of the seru:n were packed, and an automobile was off for a flying-field near New York. Speed records were broken, and the air mail carried the only known remedy to the Western Coast in a couple of days. As a result, the invisible enemy was put to rout. The quarantine was raised in a few weeks, with the death count less than 40. HRILLING incidents such as this, and the more recent race with death across the Alaskan snows, of course are infrequent in the war that science is waging against destructive bacteria. Yet it is such a gigantic struggle that its underlying dramatic elements are un- escapable. It is a wonderful warfare, according to Milton Campbell, president of the H. K. Mulford Company, of Philadelphia, towhom I am indebted for most of the material contained in this article. All its forces are directed along ultra-scientific lines, for the saving of human lives. It deals not only with the sick—those actu- ally in the grip of bacteria—but with the Protection of millions of persons still dies and killed bacteria. The uninfected but moving among the hazards _ ready-made antibodies attack the disease of disease. that affects the patient, while the killed The scientific prevention of disease is bacteria stimulate the cells to produce revolutionizing medicine. Medical men natural antibodies. of today are generally agreed that the physician of the future will devote a large VV SATEVER the nature of the virus, share of his skill toward the prevention of whether it be the microbe of infectious diseases, not alone by sanita- plague, dysentery, cholera, typhoid, the tion, but by actual immunizing of his virus of rabies, or the toxin of diphtheria, patients. or whether the microbes are killed or Compare the present and past history living, this process, known as sensitiza- of disease and you will be struck by the tion, confers on them properties that progress being made in immunology. (Continued on page 138) Giving Their Blood From the blood streams of these fine animals science painlessly draws the priceless serum that imparts immunity Mortality statistics bear eloquent testimony to the marvels immunology has accomplished with smallpox, hydrophobia, cholera, bubonic plague, and other diseases of the same malignant type. Two principal weapons are employed by science in the cure and in the prevention of disease by Then, in the laboratory, the serum is separated from the red immunology — bacterins blood corpuscles and purified to make it safe for injection into and serums. A bacterin the blood of persons, there to crush invading microbes of death

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POPULAR SCIENCE MONTHLY MAGINE, for a moment, that senger airplane, riding across the sky thousands of feet above the earth. Suddenly comes a sharp ex- plosion. The machine dives dizzily. A moment or two thought of certain disaster PARACHUTE flashes across your mind, the pilot pulls a lever and, ’ with wings and motors released, floating safely to earth. . fed you are seated in a great pas- In Emergency the VW ings Drop off and the Body Unfolds By Truman Stevens BOLTS Secure from disaster—How the ingenious airplane-parachute might appear in flight, and as unfolded into a huge umbrella, Contrast with the plane crashing in flames in the background Amazing Plane Its Own Parachute The secret that lends practic. ability to the invention lies in the manner in which the separable parts are held together so that they can be released almost in- stantly. The fastenings are screws with interrupted threads, which may be more, you think, and it will MOTOR SAILS OPEN locked together or unlocked be the end. CONTROL FOR AUTOMATICALLY simply by one-eighth tum But at the instant the RELEASING RELEASING AFTER RELEASING of the screw. The entire mechanism for releasing all the various fastenings is a controlled by the pilot ina to your amazement, the wings, motors, gasoline sides of the fuselage itself cockpit. begin to open outward in segments, like orange peel. In the rush of air, these segments, joined by webs of strong canvas, and all hinged to a center shaft at the rear, quickly open wide to form a gigantic umbrella. [NSTEAD of crashing to almost cer- tain death, you find that you are still riding easily in the same comfortable chair. The breathless plunge downward has ceased. Now you are floating earth- ward gently under the dome of a giant parachute. Just such a combination airplane and parachute, amazing in its conception, yet astonishingly simple in design, is the recent invention of Captain Lepinte,. a French aviator, who has gained distinc- tion for the production of several other safety devices for airplanes. Stripped of its superstructure, the flying machine is an immense folded parachute in itself. The same lever simultaneously releases the parachute single operation. tanks, and propellers fall PILOT'S 7 a ‘ ae "THs. simply by swing- away from the streamlined SEAT CENTRAL PASSENGERS’ ing the handle of a fuselage. Simultaneously, AXIS SWING CHAIRS, lever, the pilot can separate as the wingless car plunges Design of the machine. The shaded portion represents the wings, power the wings, motors, and pro in a nose dive, the rounded plant, and gasoline tanks, all released by a control lever in the pilot’s pellers from the fuselage. The same movement re leases the segments of the FOLDING EE ae ve fuselage covering that open outward to form the parachute. The complete re lease requires not more than a few sec onds. To prevent the big umbrella from turning inside out, wire stay rope chute with the nose end of the center shaft. Danger of the plane’s catching fire after an accident in the air would be obviated by the release of the fuel tanks. An interesting feature of Captain Lepinte’s invention is the manner i which he provides that the passenges shall remain seated upright in their chain even when the nose of the car is pol downward. He has designed the seats®# that they are attached by pivots tote How the sides of the airplane body, joined by. canvas webs, open to form the parachute. Notice how the passengers’ seats, pivoted on the center shaft, swing automatically to an upright position as the nose of the machine points downward after the parachute is freed center shaft of the fuselage. Thus, Whit ever angle the fuselage takes, the chairs always swing to an upright position. Captain Lepinte estimates that thea would descend with a velocity of mé more than nine feet a second. connect the outer rim of the pare §

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il, 1925 ite ; practic. ies in the separable - so that most in- ings are terrupted may be unlocked zhth turn ‘he entire leasing all enings is pilot ina by swing- ndle of a n separate 3, and pro- . fuselage. ement re nts of the utward to mplete re a few sec- orella from stay rope the para § the center ’s catching r would be fuel tanks. f Captain manner it passengers their chairs - is pol the seats vots to Thus, what , the cha osition.. that the cf ity of mu April, 1925 Airplanes Hurled to — Bits in Test ‘ Terrific Crashes Against =~ Wall Show Faults By Newton Burke ITH crashes that echoed through W the surrounding country for miles, four airplanes recently were hurled to destruction down an in- cline and against a concrete wall at Wilbur Wright Field, Dayton, Ohio, in a spec- tacular test conducted by Army Air Service engineers to ascertain the prin- cipal structural weaknesses of aircraft and to determine the causes of airplane col- lapses, as well as explosions and fires in fallen planes. The four planes selected for the test were old and of obsolete models. The wings were removed to prevent the planes from rising. The machines were sent away separately from a concrete platform 25 feet high, from which an inclined track led to a concrete wall 100 feet away. Each plane was lashed to the track, and its main gasoline tank and the gravity tank on top of the fuselage were filled with 100 gallons of gas. Then the motor was started, the throttle was thrown wide open, and the rope that held the craft cut with an ax. Immediately the plane plunged for- ward. Gathering momentum with each revolution of its propeller, it attained a speed of more than 100 miles an hour be- fore it reached the bottom of the incline. The crash heard as each plane in turn struck the thick wall of concrete was terrific. Bits of wood and metal were cast high in the air. In one case a small sliver from a propeller rose 1000 feet in the air and fell 100 feet away. A spray of gasoline drenched photographers and en- POPULAR SCIENCE MONTHLY Headed for Destruction—One of the four pilotless test planes at the top of the incline, just before plunging downward and crashing into the concrete wall seen in the distance gineers who were watching the demonstra- tion from shelters 25 feet away. In each case the propeller shaft em- bedded itself in the concrete to a depth of about a foot. The frail propeller was re- duced to splinters. Each plane re- bounded slightly from the wall, then crumpled into a shapeless and shattered mass of metal. In one respect the test failed of its pur- pose—no plane caught fire or exploded. Army engineers stated afterward that the cause of fire and explosion in planes that have crashed to earth is highly mys- terious. Usually, though, it occurs in planes that have des- cended in a nose dive. Crashing in this position causes the entire structure to be deluged with gasoline, thus readily starting a fire if sparks occur. This method of descent was not reproduced in the tests, the runway down which the planes sped being in- clined at a comparatively small angle. The army engineers are not yet ready to announce the results of the tests re- garding structural weakness of aircraft. The Crash—and What Was Left In the tremendous impact between speeding plane and thick concrete wall, splinters of wood and metal were flung high in the air. A shower of gasoline drenched the photographer who took the remarkable picture at the left. The thunder of the crash was heard for miles. The plane rebounded slightly, and crumpled into the shapeless mass of metal shown above

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Blasting a River Channel—A Man-Made Geyser Dynamite now can be put to work in water as well as in earth or rock. This spectacular photograph shows how tons of water were hurled a hun- dred feet in the air during the blasting of a channel in Cotee River, near Port Richey, Fla. The completed channel, 20 feet wide and seven feet deep, connects the Cotee River for navigation with the Gulf of Mexico mite—enough to blow up New York City if carefully placed—went off one day down in the mountains of Vir- ginia. With the touch of an electric but- ton a mile or two away, the detonating spark darted with incredible speed through hundreds of auger-like borings in the vast pile of rock and earth, touching the metal caps embedded in thousands of dynamite sticks. With a single impulse these chemical contrivances let loose their titanic force, lifting the whole mountain from its base and toppling i over into a deep gorge adjacent. Thus the mountain, upside down, formed the foundation for a great dam— a structure that would have required enormous masonry work otherwise, far down in the depths of the canyon. On the lowlands not far from this somersaulted mountain, I stood the other day and watched a crew of men place dozens of dynamite sticks in the ground in a straight line, perhaps six or eight feet apart. Dynamite sticks are round and GO nite en thousand pounds of dyna- POPULAR SCIENCE MONTHLY April, 1925 The TAMING How this terrible giant has It lifts huge mountains and innocent looking, as thick as two fingers, and a few inches long. They look like compressed saw- dust, stuck together with mo- lasses, maybe. Why the sticks should be put in the ground in such a way might not be apparent to the easual observer; but presently there came a quick staccato noise, as if a row of soldiers in some hidden trench had fired their guns almost in unison. Along that straight line where the sticks of dynamite had been, a great upheaval of dirt rose perhaps 10 or 15 feet, falling in a dusty shower. And then, when the cloud had set- tled, there was re- vealed something almost magical. Where the line that marked the dynamite had been lay a ditch, four or five feet deep and wider than that at the top—a drain- age channel almost as neatly dug as if a hundred laborers had toiled for days with picks and shovels. Long - time re- search work has made it possible within the last year to do things of this sort, along highly specialized lines. Scores of scientifically trained men spend their lives prying out of science explosives of kinder disposition but of greater capacity. To learn something about these men and their work, I went to the experi- mental station of E. I. Du Pont de Nemours & Company near Wilmington, Del., and there Dr. C. M. Stine, Director By Robert of Chemical Research, showed me some of the magic that modern research has wrought in taming high explosives for the every-day uses of man. He showed me how amazingly the giant dynamite has been harnessed to save time and labor. “Vast improvements have been made in commercial explosives within the last 20 years,” Doctor Stine told me, when | referred to the ditch-digging job I had witnessed. es you may think that dynamite works fast in this sort of excavation,” he said; “but relatively the time required for the wave of explosion to run along the line of the ditch is long—maybe a good fraction of a second. “The control of the speed of explosion is an important phase of the work with dynamite. It may seem grotesque to say that dynamite may be slow or fast. But apparatus has been devised for measuring the rapidity of explosion where the veloc- ity is three or four miles a second. ‘To the every-day spectator the whole How Dynamite Cut Off a Chimney Top Clipping a five-ton section from the top of a steel stack at Gibbstown, N. J., was accom- plished recently with dynamite almost as neatly as if it had been sawed off. The uppet picture shows the falling section in midair. Below: How it looked when it struck the earth geri tan eve imp slov int exp) fact with “ [’ tern mite for 1 non- of th Int dyn: belo next thro year poss The road ice 2 dyné the | New pape wate mite teleg ina ular of lo only flood

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1925 ert some h has es for howed Lamite e and Made he last when I I had » works mn,” he equired ong the a good plosion rk with e to say t. But asuring e veloc- e whole — april, 1925 POPULAR SCIENCE MONTHLY of DYNAMITE been put to work for us— cuts wood into stove lengths Bracefield series of explosions seems almost simul- taneous. To the research chemist, how- ever, the difference in speed is of great importance. He can quicken the wave or slow it down as he pleases.” Doctor Stine described recent progress in removing the danger of handling high explorives in large quantities, citing the fact that in New York State is a seven- mile ditch dug cooperatively by farmers with dynamite. “TN THE old days,” he reflected, ‘“‘you I recall reading of the laborer who ex- terminated himself while thawing dyna- mite. The elimination of the necessity for thawing, through the production of a non-freezing dynamite, is one illustration of the work the scientist has accomplished. In the iron-ore country, non-freezing dynamite now is used at 30 degrees below zero.” E Out on the highways of the Rockies next month, automobiles will get through with ease, where in former years motor traffic was often im- possible before June, or even July. The modern method of opening such roads is to bore into the dense mass of ice and snow and break it up—with dynamite. In the same manner ice jams in the rivers are blasted. In northern New York State not long ago a huge mass of ice formed above a large paper mill, and the impounded waters menaced the plant. Dyna- mite was shipped in response to a telegram, and the ice was dislodged ina day. Quite as spectac- ular is the blasting of log jams that not only threaten to flood whole regions, but prevent the logs from floating to the sawmills. Here again dynamite comes to the rescue. It always lets loose the bar- ricade. In ordinary wrecking jobs, too, dyna- mite now does, in a few seconds, the work that formerly required days. In a college town, not long ago, a towering old brick smokestack alone remained of an erst- while factory. For years it had disfigured the college settings. At last the contract was let to have it taken down brick by brick—but a dynamite contractor offered to remove it at a small fraction of the price involved by the other method. Be- ginning with small charges near the base and gradually enlarging the opening, he felled the huge chimney as accurately as the woodsman fells a tree, along a given Testing Explosives This laboratory apparatus, known as a nitrometer, is employed for testing the inflammability of ni- troglycerine, guncotton, and nitrate of soda How the Force of Dynamite Is Measured Another testing apparatus, the ballistic pendu- lum, measures the explosive force of dynamite. The percussion is made to act against the ball of a pendulum, causing the pendulum to vibrate. The amount of vibration then is measured on a calibrated arc, registering the force expended Safe to Handle Most of us think of dynamite as something extremely dangerous to handle. As a matter of fact, ex- perts can cut it, scrape it, burn it, and even drop it without its ex- ploding. Thousands of tons of it are transported every year by railroad, wagon, and motor-truck line. So close was the reckoning that it had to graze one of the col- lege buildings in its descent. Quite kindly is the dynamite that cuts from the hillside slices of white or polychrome marble. Once upon a time the individual workman quarried these slabs with infinite labor. But now small charges of dynamite are inserted along an indicated line and exploded simul- taneously, with a gentle dynamic tap. Yet it cuts out the slabs as neatly as the old-time quarryman could do it. Almost benign also is the dyna- mite used for tree planting. ““On one oceasion,”’ Doctor Stine told me, ‘‘a group of women gathered for this purpose, and not knowing that dynamite was to be used they stood about the work- men as the sticks of explosive were cut in pieces. They began to inquire what the stuff was, and fled in disorder when they found out. ” a ae the dynamite was placed in the hard soil and exploded, there was just a murmur and a tiny upheaval of earth over each charge. But the soil was loosened far down into the ground. Not only was the planting accomplished with ease, but the young roots had every chance to grow easily. “This particular use of dynamite has become widespread, in the setting out of orchards, for example. Moreover, ex- traordinary results are on record where orchards had practically ceased bearing and were rejuvenated through the loosen- ing of the soil with dynamite. ‘Dynamite is an adjunct of farming in cut-over regions, where whole fields are freed from stumps in a few days. Con- tractors go even further and split the wood

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How a 100-year-old farmhouse was completely razed by a dynamite blast. Only a stone pile remained into stove lengths at the same time. In Florida a large grower of vegetables found his whole crop in imminent danger of ruin by water that backed up over his land after torrential rains. He called in a dynamite contractor, who told him that the small ridge that held the water could be blown away and the crops saved, but that the rush of water probably would carry away a small bridge over a creek below. The grower guaranteed to replace the bridge—and the job was done in a few hours. - His crop was saved. “Subsoiling via the dynamite method is now widely employed.. Twenty million pounds of explosives are uSed every year for agricultural purposes.”’ lel MINING, of course, explosives play an exceedingly important réle. Here, though, their use in the past has been surrounded with hazards that have pre- sented extremely difficult problems. If you could watch the dynamite research men in their investigation of these mine problems, you would find a huge steel chamber, called a “gallery,” which duplicates the dust and other conditions in the mines. This atmospheric content of the mine has been scientifically manu- factured and let loose in the gallery. Now watch the dénouement. With the gallery sealed and the scientists watching the indicating devices at a safe distance outside, a tiny spark is flashed over a wire, and the muffled explosion in the chamber exemplifies the actual blasting underground. Now the scientific appa- ratus measures all the gases exuded. Of course, the problem is to manufacture ex- plosives that will cut down toxic fumes to the minimum. ‘All through the experimental work with dynamite has run never-ending research to make this explosive safer,’’ Doctor Stine told me. ‘‘To start with, we had the treacherous nitroglycerine, an oil that had a habit of exploding on the least provoca- tion. It was once used in large quantities despite its terrible disposition—particu- larly in the oilfields. Specially designed FILLING INSULATED GRIDGE WIRE, WIRES

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COMPOSITION PLUG COPPER SHELL The Detonating Cap The cap is filled with fulminate of mercury, through which is bridged a metallic filament, finer than a hair. A minute electric current makes this fine wire red hot, firing the charge EXPLOSIVE” POPULAR SCIENCE MONTHLY

wagons transported it, with all sorts of cushion arrangements; yet not infre- quently serious accidents resulted. ‘““Today this same nitroglycerine, with all its old appalling force, has been har- nessed into the compound called ‘dyna- mite,’ so you can cut it, scrape a hole in it, burn it, or even drop it. The explosive is

April, 1925 transported Safely in great quantities on the railroads, and even Zoes through wrecks without exploding. ** All this has not come about accidentally. It jg no mere question of pouring the nitrogyleer. ine Into sawdust or some other absorbent, ang molding it into cylin. drical sticks. A mogt extensive chemical ra search has done it. To. day the manufacture of high explosives Stands twelfth -in the list of hazardous occupations. “Some of the ordinary constituents of dynamite, aside from sawdust, are wood pulp, cornmeal, flour, sodium nitrate op sulphur, combined with high explosive compounds that have been built up in the chemical laboratory with a view to ob- taining a chemical molecule especially adapted to industry. ‘“‘Much of our advance in producing better high explosives is due to scientific control of the chemical reactions of com- plex chemical compounds. Large-seale chemical reaction is no longer a matter of individual judgment. The rate of mixing ingredients, the quantities and the tem- peratures and pressures are controlled to the fraction of a degree. Mechanical de vices make the manufacture as fool- proof as possible. “THEN, after all other problems have been considered, the research man is called upon to produce dynamite on a commercial basis. It must be made cheaply enough to be marketable. In hig search for cheaper high explosives, he has competed with nature in the synthe sis of the raw materials that constitute the starting point in high explosives. For example, the glycerine forming the basis of many nitrated compounds used in dynamite is usually obtained as a by- product of soap. The research chemist has perfected methods for producing artificially a glycerine identical with that occurring in the animal fats. ‘*Sometimes sugars are used in making (Continued on page 143)

Felled by Dynamite Dynamite charges set . off around the base of this brick chimney chopped it down almost as accurately as a woodsman fells a large tree NEW CHANNE 1800° (200,000 CU L NEW CHANNEL > YDS) 3600'(300,000 CUYDS) S

NEWLINE ~~=2222>-7

ALLEGHENNY DIV.C&O-OLD LINE

Changing a River Kos The map shows how new P channels were dug by dynamite for the mean- dering Jackson River to provide a straight right- of-way for the Chesa- peake & Ohio Railway near Clifton Forge, Va At the left is an irriga- tion ditch dug by dyn& mite. The sticks of dynamite were placed at six-foot intervals

April,

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» 1925 Y in n the 1 goes ithout come . Itis mn of Yleer. " Some Most al re - To ure of stands ist of ations, ants of wood ate or losive ‘in the to ob- ecially ducing entific f com- e-Scale tter of mixing e tem- lled to cal de- > fool- s have h man eona made In his es, he ynthe- stitute Ss. For e basis sed in a by- hemist ducing th that naking L

River yw new ug by mean- iver to - right- Chesa- ailway re, Va. irriga- dyna- ticks ervals ‘mum elevation, the periscope’s radius of POPULAR SCIENCE MONTHLY 35 april, 3925 New Buoy Periscope Sees and Hears Flashes Pictures to Submarine / gem. 2000 Yards Away PERISCOPE ON BUOY \_ WHICH DETACHES FROM DECK GE SUBMARINE AND FLOATS ,ObSURFACE

meee oe See a aa ee Ww Re ie Instead of being an integral part of the submarine, Dr. V. A. Clarke’s When not in use, the device is carried in the superstructure. Pictures ingenious electric periscope is mounted on a buoy, which floats 2000 and sounds of approaching vessels or airplanes are transmitted electrically yards from the conning tower when an observation is being made. to the observers overt a copper cable, which also controls the buoy N AMAZING new type of peri- (CUT 7]_~Ss cable. These impulses are received in the scope, which floats on the surface od conning tower, where they are reconverted far away from the submarine and +e into light waves by a reverse of the trans- carries to the latter views of the surround- ing sea by means of principles similar to those employed in the radio transmission of pictures, has just been taken under consideration by the U. S. Navy Depart- ment. The periscope is the invention of Dr. V. A. Clarke, of New York City. Its purpose, of course, is to permit a sub- marine to observe without the possibility of detection by surface ships. According to the inventor, the device doubles the efficiency of a submarine. The periscope is mounted in a cigar- shaped buoy, about 12 feet long and three feet wide. When the submarine is under way, this buoy fits into a compartment in the superstructure. When an observa- tion is to be taken, the buoy is released, and is towed at the end of a copper cable 2000 yards long. Electric controls in the conning tower of the submarine permit the periscope to be raised or lowered by varying the water ballast of the buoy by pumping. Other controls operate an electric motor by means of which the device may be rotated through 360 degrees. At 14 feet, its maxi- X <deue i at : a ‘ mitting process, and viewed on a screen. ec eget : The images produced in the submarine by “Ek : this method are said to be accurate enough not only to identify the objects PEBISCOPE that cause them, but to enable the sub- marine to fire upon ships seen through the long-distance periscope with every chance of hitting the mark.

HIS type of periscope not only can “see,” according to its inventor, but also “‘hear.” The latter operation is effected by supplying the device with a sensitive microphone and amplifying ap- paratus whereby sounds such as are made by the motors of airplanes oer the propellers of approaching ships are heard in a receiver in the conning tower. The electric periscope, according to Doctor Clarke, would insure safety to the occupants of a submarine by guarding the craft against attack by enemy vessels. If the observer found the periscope sur- rounded by hostile ships, he would cut the cable con- necting it with the subma- rine, and leave the periscope behind as a blind while the submarine escaped. Doctor Clarke also asserts his in- vention might be used as an automatic sentinel to warn vision is said to be 11 miles. BENEAT H the periscope tube is a series of selenium cells connected with a sort of radio transmitter. An image of = whatever the periscope ‘“‘sees” falls upon ; coast-defense fortifications these cells? and the variations of light ten yl gh ag of coming attack from the intensity due to the shadows and high water ballast. At its full sea. His device, he states, can be built lights of this “ picture” cause correspond- height, 14 feet, the range of vision is 11 miles. complete for about $15,000. The ordinary ing variations in electrical impulses that |“ Microphone and amplifying device transmit = telescope type of periscope costs between é sounds to the submarine or to a station on the pass to the submarine through the copper shore, adding greatly to the submarine’s efficiency $8000 and $12,000.

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36 POPULAR SCIENCE MONTHLY April, 1925 Apel Newest Weapons for Fire Fighters | = French Motor-Car Engine Pumps 24 Streams of Water a a & i» | % “j § i ee i ee A L) ¥ Pages All from One Engine Cs This spectacular photograph shows firemen in Paris demon- strating the latest fire-fighting equipment. Twenty-four streams of water are being pumped from the Seine River by the recently devised single engine shown at the bottom of this page. Paris claims to have the world’s most effective fire-fighting system Protected from Smoke Paris -firemen are equipped with a new type of mask that is said to afford complete pro- yy. tection from smoke and fumes : fairl; “fy didn broa Trailer Pump ‘stiff An extremely light I and compact pump- ; 1 ing apparatus just iden constructed for rural the ¢ fire departments in and England is mounted Of on a trailer that can actu be hauled to the him scene of the blaze by | any size motor-car a ame that e arou Motor-Car Fire Pump phe It looks like a limousine, but this run: machine is really a very powerful inst new type of fire pump recently put spot into service in Paris. With a four- coul broz { Bi eye don ciple | cam, coul cane v4 not Fs: = the ‘Soh 4 = 3 easil Chile a a a : y a the : i =e heat A Dizzy Climb Thee T Among the most important ~ tive pieces of modern fire equip- Be 'Z = 2 eyes ment, especially in large cities ; i e kee] with tall buildings, are the ex- F whil tension ladders. This one, in . a | Paris, rises to a height of cylinder engine it is capable of delivering 24 _ the large hose seen at the left of the picture. te nearly 100 feet. This view high-pressure streams of water. The water Notice the battery of hydrants at rear no’ shows French firemen in action is pumped from the Seine River through car, to which the fire hoses are attached oth

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, 1925 rs cture. ached Apeil, 1925 +h of these two houses js broader? The one at the you will say. Yet actually they are both the game size. The reason one tall and narrow, the . and broad, lies in ' eed lines that de- i ceive the beholder’s eyes 4 POPULAR SCIENCE MONTHLY Do Your Eyes Tell You Lies? How the tricks of vision can be used to make fat people look slimmer, big feet appear smaller, or to make your home and its rooms more attractive—Try these tests on yourself and see how your eyes can fool you country with me the other day, was remarking on two houses set fairly close together by the roadside. “T wonder,” he said, ‘‘ why the builders didn’t make that first house low and broad like the second. See how tall and ‘stiff’ it looks.” I looked at the two houses and smiled. “Those houses,” I replied, ‘“‘are identical in size. The difference lies in the eaves, the windows, the chimneys, and the small extension.”’ Of course he didn’t believe me. I actually had to get out and prove to him by rough measurements made across the lot fronts that the houses were the same. It did seem impossible that putting half a dozen low shrubs around a house and cutting an extra sized window (so as to make your eyes tun sideways to take in all the windows instead of having them appear as spots) and lengthening the eaves could make a stiff, prim house look so broad and cozy. But I had studied how to trick the eye and I knew how easily it could be done. I had seen many curious prin- ciples put into practice in marine camouflage, principles that we never could have made work if the eye were not fairly easy to deceive. The fact is, the eye can be tricked much more easily and much more completely than the ear, perhaps because the organs of hearing develop earlier than those of sight. _ When we are frightened, we instinc- tively stop and listen. In the dark your \ FRIEND of mine, riding in the eyes are practically useless, but vour ear keeps on working just the same. Even while you are asleep your ear keeps guard, a little drowsily perhaps, but awake enough to give you warning before any other sense will. Therefore, within the By Alon Bement Professor Bement, a young American artist, is one of the world’s foremost authorities on op- tical illusions. During the war he worked for the government in cam- ouflaging American ships. He is now director of the School of Fine and Applied Arts of the Maryland Institute, Baltimore. \ y VERE q d How Diagonal Lines Deceive range of its proper functions, the ear is considerably more to be depended upon than the eye. We often are not conscious of the de- fects of the eye until we begin to consider the matter seriously, but at a very early age we have learned to interpret the illu- sions that confront us almost withou’ thinking about them. During the war, one of the earliest discoveries that we made was that we could reduce the visibility of objects on the land by painting them to re- semble the, objects about them, but when we tried to do the same with ships, we found that it wouldn’t work. The submarine had only to get the ship between it and the sun, and there you were—outlines as clear as any- thing. Besides that, the atmospheric conditions of the sea change so often and so greatly that you couldn’t count on any given condition. You’d paint your vessel to be invisible in a green sea and the ocean would turn gray or purple. S IT didn’t work, we had to try something else. The next time Fig. 1—Diagonal lines running upward make the rectangle at the left appear to taper toward the top. The perpendicular lines in the right-hand figure seem to converge toward the top, yet actually they are parallel. The same principle is applied in uniform to make the hips of the wearer appear narrower and, by force of comparison, his shoulders broader we went to the opposite extreme. We wanted the ships seen—the more vividly the better. The reason for this was that the submarines did not attack from a distance. When a sub- marine sighted a vessel, it remained on Fig. 2—Does the border of this rectangle look straight or curved? Here again the trick of diagonal lines makes the rectangle appear to bulge at the center and taper at the ends. Yet the outside lines are parallel the surface long enough to get the size of the ship and her exact course, and having made its calculation on where the ship would be in 15 minutes, it submerged and headed under water for the place from which it could attack at close quarters. We discovered that we could throw out the calculations of submarine pilots by deceiving them as to the direction the ship was taking. When we found that we

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' 38 could conceal the true perspective of a vessel by the way. we used lines, spots, and colors, we wanted the lines, spots, and colors to show up as brightly as possible. The submarine judged the course of a ship by its perspective lines. Wherever possible we distorted these lines; we pinched together or widened the natural lines at the bow or the stern, or made wide marks across them,so as to conceal the true shape of the ship and thus in the end make its speed and course difficult to compute. OMETIMES we tried to make them look long, sometimes short. The fast vessels we painted to look short and stubby, and we tried to make the slow freighters look as slim and fast as we could. As a result of this sort of camou- flage a number of submarines, in the last Which Man Is the Tallest? You'll find it hard to believe that these three men all sre the same size. Yet if you measure them with a ruler, you'll find that they are. Your eyes are tricked by the fact that every- thing in the picture has been drawn in per- | spective except the three human figures few months of the war, so miscalculated the speed and direction of vessels they were attacking, that they came up too close to them, and being unable to train their torpedoes fast enough were promptly run down or captured. Just to see how effective it was, and how your eyes can be deceived, try out on yourself the surprising tests shown on these pages. If you have any faith in your eyes, for example, Figs. 3 and 4 probably will re- move the last vestige of it. Here are two striking examples of things that seem to change while you watch them. Do you see the top side of steps in Fig. | 3 going up, or the under side of steps going down? ‘Look again. What do you see this time? Maybe you see just a design in black and white. Now, just what do | you see in Fig. 4? Is there a solid block A with the top toward you on the right, with a kind of wing and an open space or . hollow at the left? Or do you see the solid to the left and the hollow space to the | right? Or do you see two solids set at an angle to each other? Observe this solid POPULAR SCIENCE MONTHLY no They Change before Your Eyes Look closely at the steps in Fig. 3 for a mo- ment or two. Suddenly you will see them turn upside down before your eyes. You will find that your eyes play the same amazing trick with the chimney-like object in Fig. 4 © Do you see the pyramids in Fig. 5 pointing toward you or away from you? Watch them a moment. You will see them change while you look. Which circle in Fig. 6 looks larger? They’re really the same size, surprising as it may seem. And in Fig. 7 does the perpen- dicular line at the left look longer than the one on the right? It isn’t. They’re the same length. Your eyes merely have been tricked by slanting lines, in one case pulling your sight beyond the ends of the line, in the other pulling your sight in toward the center Legs that Fool You You'll swear that one of these men is bow- legged, the other knock-kneed, won’t you? Now hold the page on a level with your eyes and look along it from the bottom edge. You will see that all four legs are perfectly straight carefully. Does it seem to slip over to the other side while you are watching it? It is an odd sensation to see it change right before your eyes, is it not? These are examples of what is called “ambiguous perspective,” the principles of which we used during the war in paint- April, 1995 ing ships. These curious coats of Vari colors were put on, not to render the shi invisible, but to deceive the enemy ag the size and shape and the cours . pursuing. e it way If you will hold your hand before you silhouetted against a bright areg like a very bright sky, you will see, ig yo move it swiftly to the right, a bright en just behind its back edge, and outside that a dark shadow, a sort of a ghost of the hand itself. T TAKES a keen eye to see this phe. nomenon under the most favorable cir. cumstances, but we are told that the light and pursuing shadow are always just be. hind any swiftly moving object. This ig the reason we cannot see a really swift motion. The dark edge following goty confused with the real edge. The camer rarely reveals this, and that is one reason it can show things the eye cannot see, If the fast camera can eliminate this confy. sion of edges, there seems to be no reason why science may not one day hand usa pair of eyeglasses that will do the same, We have glasses to correct far sight and near sight. Why not glasses for swift sight? You can be deceived just as easily with color as with line. If you take a deep red Which Neck Looks Longer? The man with a long neck usually seeks to make it look shorter by wearing a high collar. Actually the high collar makes it look longer. The necks in the picture are the same length background, look at it for a while; then place strips of gray paper against it, the strips will appear a ghostly sort of green; On a blue surface your strips will look orange. Easier than that, try looking ata strong electric light for a few minutes, then look at a blank wall. You'll see the light exactly the same shape, but the color will be purple. A BOOK on dress recently warned against wearing too much orange, because it gave blue shadows to the face. Primary colors—red, blue, yellow, green, orange, and purple—have a tendency .to make us see their opposites. In other words, wherever you see one of these, its complement will be hanging around and you will catch glimpses of it now and then out of the tail of your eye. So, you see, your eyes can’t be trusted. Things are not what they seem. At first it may appear rather a low trick for your eye to play you; but when you think about it, I believe you will agree with me that it is a fair arrangement. If the eye could not be tricked into making hi spaces seem low, and broad ones slim, you would have to go on living with you imperfections. But with an understanding of the law of tricking the eye by subtle placements of lines and colors, it is po (Continued on page 145) oe

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, 1925 aTloug © ship a8 to it wag re you a like if you ht line le that of the is phe. ble cir. 1e light ust be- This ig Y swift 1g gets camera Teason see. If 3 confu- ) Teason nd us q e same, ght and or swift ily with leep red vile, then st it, the of green, will look yking ata minutes, ‘ll see the but the r warned h orange, » the face. yw, green, idency .to In_ other these, its ound and y and then ye trusted: . At first k for your you think .e with me If the eye king high s slim, you with your erstanding by subtle , it is poe april, 1925 Why the Eclipse Was Late How Science Is Adding, Little by Little, to Our Knowledge of the Sun N LAST January 24 occurred what O was in some respects the most remarkable eclipse of the sun in the history of the world. More people undoubtedly saw that eclipse than saw any previous one, for the reason that the path of the moon’s shadow was across territory more thickly populated than any that the shadow ever had traversed. Likewise, in the path of totality stood a larger number of astronomical observatories than ever before were situated in the path of a single eclipse. Because of available con- veniences of transportation, many Amer- ican astronomers whose permanent sta- tions lay outside the path of totality found it relatively easy to move their instruments and establish temporary sta- tions at places from which the phe- nomenon would be visible in its entirety. Clear skies virtually throughout the path of totality facilitated observation of the eclipse in all its phases both to scientists and laymen. Due to recent develoc¢ments in the science of aerial photography, it was the first eclipse in history of which the world was assured of permanent photographic records no matter what the weather; for, if the day had been dull, airplanes could have ascended high above the clouds and the photographers snapped the hidden sun in the mistless light of the upper atmospheric strata. LSO, at least one entirely new and “ unique investigation was made when Science seized the opportunity offered by the eclipse to study the mysterious effect of darkness on radio transmission and reception. In short, Nature arranged and carried out the details of the eclipse like 2 master stage director, and supplied at one time a Gorgeous spectacle for the layman and Raymond J. Brown POPULAR SCIENCE MONTHLY By The Sun in Total Eclipse A remarkable photograph of the eclipse of the sun January 24, made by the 62-foot camera (at left) of the Swarthmore College expedition at the Yale University observatory. It gives a spectacular view of the corona extending hundreds of thousands of miles into space. In the original photograph the diameter of the moon measured about 7!4 inches the means of making the complex observa- tions through which astronomers have learned all that they know about the sun. The program was a little late in starting, but that was expected, because eclipses, for reasons that will be explained pres- ently, never occur exactly on time; they always arrive a little later or a little earlier than the time predicted. And so it would seem that with condi- tions so favorable this eclipse ought to have yielded a wealth of new scientific knowledge regarding the sun. Possibly it will. At the present writing, however, approximately a month after the eclipse, science has but little to report, the reason being that knowledge of the sun is wrung with almost incredible slowness and diffi- Photographed from the Air An airplane picture of totality made from a height of 18,000 feet by the Fairchild Aerial Camera Corporation. Note that the moon appears egg-shaped. This distortion is due to the fact that the airplane was moving rapidly when the photograph was made. If, however, the day had been cloudy, preventing ground cameras from snapping the spectacle, airplane pictures such as this would have been invaluable for astronomical study culty from the observations and photo- graphs made at time of eclipse. In fact, the long and complicated calculations and measurements incidental to compil- ing the mass of data recently obtained scarcely have been begun. Professor John A. Miller, director of the Sproul Observatory at Swarthmore College, Swarthmore, Pa., leader of an expedition that observed the eclipse from the grounds of the observatory at Yale University, New Haven, Conn., explained to the writer a few days ago why new knowledge of the sun is so rarely obtained. s HAT we know of the sun,” he said, “is the cumulative results of thousands upon thousands of observa- tions made during hundreds of eclipses and at other times. No one eclipse can be expected to yield results of a startling kind. As an example of the slow way in which things move with regard to the sun, take helium. This element was discovered in the corona of the sun during an eclipse in 1868. Almost 30 years passed before it was learned that helium was a terrestrial element also; and it is only now, a quarter of a century or so later, that man is finding a useful application of helium in the inflation of airships. “There was no discovery made at the recent eclipse comparable in importance with the discovery of helium. Of that we are certain. Just what information of a really important nature the eclipse will yield we shall not know for months prob- ably; years, perhaps; at least until we have completed the measurement of our photographic data and our calculations. “Our photographs already have dis- closed one fact of’interest to the astron- omer—namely, that although it is only 21% years after the minimum sunspot period, the shape of the corona shows that (Continued on page 141)

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If you are in the path of a lusty sneeze such as this you are more likely to catch cold than if you are exposed to severe weather or get your feet wet. For the common cold is extremely Why Colds Spread—Beware of Sneezes and Coughs POPULAR SCIENCE MONTHLY April, 1925 =~ COLDS By Malcolm MacDonald ratio declines, until the last days of the year show the average-line within hailing distance of the lowest point between October 1 and June 30. This comes at season when Massachusetts is jn the midst of a New England winter and New Orleans, La., Tucson, Ariz., and San Francisco, Calif., are living outdoors in the sunshine. ‘Tavs do actual health records contra. dict our common beliefs about colds, The new year starts with an outbreak of colds that begins late in December, finds its peak in the early days of January, and sharply recedes before the middle of the month. From this time forward to the end of June there is a steady decline in respiratory ailments. contagious. The corpulent, overfed man in the The groups on which ti rear, who apparently is the least concerned, is H a: P b: — figures of the the one who probably is more _ susceptible ea 5 SEVIOS ae ee ued be regarded to contagion than the thinner passengers as being fairly representative of the entire population. For the greater por HEN you have a cold— and most of us have one or more each year—do you blame the weather? Most of _ us do. Miserable and wretched, we speak harshly about the weather, stay indoors, and keep our feet dry. Now wet. feet are not to be recommended at any time, but reports of a recent survey under- taken by the United States Public Health Service indicate that we can no longer be sure of our ground when we blame the weather for a cold in the head or other nose and throat disorders. This survey is the first effort of its kind to determine when, how often, and why, we suffer from colds, coughs, and allied ailments. The results seem to have upset a number of popular beliefs. Chief among these surprises is an indi- cation that meteorological condi- tions, at least during the year studied, have little bearing on the tion the survey deals with college students, among whom more than What Science Has Found 13,000 individuals were examined. Out about Colds The common cold is extremely con- College students are likely to be of the same general age. To offset this selective grouping, and to afford more intimate study of conditions in family life, the re tagious. search also has embraced groups It does not come from bad weather or of families throughout the United wet feet, but from germs that attack States, with reports covering those whose physical condition makes entire households, _ including them susceptible. Each of us, on an average, suffers from 3.7 colds a year. Colds make no distinction between youth and age. But indoor workers and city dwellers seem more susceptible to them than those who have outdoor occu- pations or who live in the country. October is the worst time of the year for colds. Another bad month is January. { June is the month in which you are least wth an likely to catch cold. prevalence of colds, bronchitis, influenza, sore throat, hay fever, and pneumonia. This lack of relationship between colds and the weather in the United States is demonstrated in the startling similarity between cold-occurrence in the rigorous North and that in the warmer South and Pacific Coast. In general, New Orleans and San Francisco suffer with Chicago and Boston—and at very nearly the same time of the year. HIS conclusion, reached by the Public Health Service, is based on reports of health conditions among representative groups of people in Massachusetts, Ohio, Illinois, Maryland, the District of Colum- bia, Louisiana, Montana, Utah, Arizona, and California, covering a period of a little more than a year. That colds have their seasonal out- breaks is borne out by a study of these reports. The indications are, however, that colds are not most frequent in the heart of winter, but that in most sections under survey the highest preva- lence of trouble comes in October. For all the centers embraced in the study the October “epidemic” was shown to be perhaps 20 per cent greater than the next highest ratio, reached in January. During the latter half. of October respiratory troubles appear to sweep from coast to coast, and from New Eng- land to the Gulf. During November and December the Indoor workers are more likely to catch cold than those who, like the telephone lineman, work in the open aif. The lineman, however, if subjected to the continued weakening effects of extreme exposure, becomes more susceptible to the much graver menace of pneumcnia Ap ser the pe

Page 17

l, 1925 ‘ & ’. ald of the hailing tween eS ata in the d New d San OTS in contra- t colds, itbreak ember, inuary, ddle of rard to decline 3 of the garded e entire er por- college re than amined, y to be ‘Oo offset and to udy of the re- groups United Overing cluding mes n aif. inued mcnia

April, 1925 How you get them, avoid them, and how to Vital new dis- coveries about this most common of man’s ailments treat them. servants. These latter groups included the families of medical officers of the army and navy, the medical and scientific ersonnel of the Public Health Service, and the faculty members of the selected colleges. nA compilations of the investigation, which, by the way, is still in progress, show that in a fairly representative group there were few in- dividuals who escaped colds during a period of 514 months. The figures also disclose that only 10 per cent escaped colds entirely. In the period studied the individual cold average was 1.9. Should the same rate obtain throughout the year in the country, it means that if you have your share you will have 3.7 colds each ear. : In the past there has been no basis for study of the prevalence of such minor ail- ments as the common cold. Such ail- ments are not included in the lists of dis- eases that must be reported to the local authorities. But by con- POPULAR SCIENCE MONTHLY how to country, there seems to be an advantage in favor of the person living away from. the congested centers. The reasons are obvious. City houses are apt to be overheated. The evidence brought forward by medi- cal observers tends to prove that where an_ indoor temperature of more than 70 de- grees is maintained during cold weath- er, there is an in- crease in respira- tory disorders. The reason for this is that in overheated rooms the relative humidity of the air, on which our health and comfort largely de-

tinued investigation the Pub-s «

lic Health Service hopes to obtain much additional in- formation as to the preva- lence of respiratory ailments and their causes. While the data so far gathered shows clearly that all sections suffer from num- bers of common colds at about the same time of year, the outbreaks in New Or- leans are entirely independent of those in Chicago, Boston, | and San Francisco. Appar- | ently there is no exchange of infection in these outbreaks.

Make Your Own Hygrometer An efficient hygrometer, or wet and dry thermometer, with which you can determine the relative humidity of your rooms, can be made easily from two ordinary household thermometers, as shown in the illustration. Simply mount the thermometers on the same board and keep the bulb of one of them moist by means of a wick tied around the bulb and dipped into a small medicine vial filled with water. The table below will enable you to determine the hu- midity from the difference in the readings of the two thermometers.

. Get plenty of sleep in ; 2. In the morning take a well-ventilated Aste ee . _ 3. Avoid overeating. Don’t ; eat too much meat or pie =

44 ee Le ee Le a ‘& & 2 * I roon | cold dip, then a brisk rub ; : 4. Take vigorous outdoor -* exercise daily, if possible Four Ways to Avoid Catching Cold pend, is likely to be unusually low. “ Rela- tive humidity” means the amount of moisture in the air in comparison to the amount that the air could possibly hold. If the relative humidity of the room is 50 per cent, we understand by that that the air in the room has just half as much moisture in it as it could possibly hold at that particular temperature. Its ability to hold moisture increases as the temper- ature is increased. [N THE wintertime the temperature of the outside air is very low, and con- sequently the amount of moisture in it is very low. When this dry air from the outside comes into the house, it is warmed. This makes it capable of hold- ing much more moisture than is already init. Consequently the relative humidity of the air in the home is very low.

The attacks come relatively LS A nips oe te sae jo In many homes the air in the winter- simultaneously. 7 M)) time is drier than the air over a desert. Another phase | / Ns Ca The results are of identity is found ul \ ll my \ that the perspira- in the duration of —————— tion from our illness. From north to south and from east to west the average length of disability for all respiratory disor- ders is slightly less than 614 days. degrees and Medical experts Dry 1 2 on the subject tell Bulb me that the com- 50 93 87 mon cold is no - a ae] respecter of years, 36 94 88 but comes to old 58 94. 89 and young alike. 60 94 89 The same may 62 04 «89 be said concerning 64 95 90 sex. Apparently 66 95 90 boys and girls, men 68 95 90 and women are hi = equally suscepti- - a a 76 4©96«OO en it comes 78 96 91 to a comparison 80 96 91

between town and The difference will be 10 degrees. Now run down the column that has the Difference between dry and wet bulb thermometers the wet bulb 60. 3 4 5 6 rf 8 S 10: 81 74 68 62 56 50 44 39 33 81 75 69 63 58 52 46 41 36 82 76 70 65 59 54 48 43 38 82 77 71. 66 61.55 50) 45 40 83° 77° 72 G7i--62 Si S52 42 42 84 78 73 68 63 S58 53 49 #44 84 79 74 69 64 60 55 50 46 85 79 75 70 66 61 56 52 48 85 80 76 71 66 62 58 53 49 85 -Sk 76 72 67 G63: SS) 55. St 86 81 77 72 68 64 60 56 52 86 82 78 73 69 65 61 57 53 86 82 78 74 70 66 62 58 54 87 83 78 74 70 67 63 59 55 87 83 79° 7S <7 G7 64) 160°.:57 87 83 79 76 72 68 64 61 57 How to Find Relative Humidity naling the dry bulb reads 70 figure 10 at the top until you come to the horizontal column corresponding to a dry-bulb reading of 70. At this point the number is 56, the relative humidity. bodies evaporates very rapidly, mak- ing us cold, al- though the room is quite warm as far as the temperature is concerned. If the relative humid- 12° 13) 14 15 ity of the home is . between 50 and 60 28 22 17 12 per cent, a tem- = - = = perature of 68 de- 35 31 26 21 grees will be found 38 33 28 24 very comfortable; 40 35 31 27 while with dry air 41 37 33 29 a temperature of 43 39 35 31 from 70 to 75 is 45 41 37 33 necessary for com- 47 43 39 35 fort. 40 | This hot ry ai 51 47 44 40 is very irritating 52 48 45 42 to the nerves and 53 50 46 43 injurious to the 54 51 47 44 eyes. It makes

(Continued on page 146)

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42 POPULAR SCIENCE MONTHLY April, 1995 W hat Huge Seas Do to Ocean Liners An Explanation of the Origin of Recent Giant Waves septeinninienaaais ~e — Cig not te * oe What Causes a Mountainous Wave—Lines I, 2, and 3 represent three separate series of waves of dif- ferent lengths. Occasionally the crests and hollows of the series coincide, piling up a huge wave, as shown at the right. Ifa liner’s nose happens to be down when she encounters one of these exceptionally large waves, she takes the all-enveloping sea right over her bows a How Most of the Damage Is the full force of beam seas crashes Done—When a large liner rolls against her sides. Because of with maximum velocity into the her weight and size, the ship has trough of one of the great waves, little “give” before sucha battering A Dangerous Beam Sea —This pic- ture shows what happens when a great liner, with nose down, rolls inward toward one of the huge waves causei by reason of three waves coinciding Why the Big Ship Gets the Worst of It —A heavy wave strikes a big liner with greater force than it does a smaller ship, because the liner offers greater resistance. The smaller ship (at left) can “give” more to the sea, as indicated by the dotted lines 5 ene gales of cyclonic fury struck Atlantic shipping during the last two months, it was noticeable that some of the largest liners were the worst sufferers. Fittings were damaged, staterooms flooded, and passengers thrown about and injured. Even on the Leviathan, the world’s largest ship, passengers were slightly hurt. The average height of waves during an Atlantic a gale, mariners say, is about 40 feet. How is it, then, ate - that waves can rise to such a height as to damage The Pitch of Ships—A long, the decks and fittings of liners often from 80 to 90 heavy liner, pitching regularly, feet above the normal water line? By the aid of does not rise quickly to a heavy picture and line the artist, G. H. Davis, has given @ wave, with the result that a deluge graphic explanation. of water occasionally pours over the bows. But a trawler, smallest of sea-going ships, quickly rises and falls over the crest of the wave

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1925 avy n it ater ve” ines tlantic it was sre the rooms njured. t ship, tlantic ;, then, lamage ) to 90 aid of riven & April. 1925 an Twin Letter-Boxes One of the boxes is for local letters, the other for domestic and foreign mail—a simple new idea that saves time in sorting at the post office business man on a Monday afternoon a few weeks ago while he was signing his day’s correspondence. “Here’s a letter that must get to San Francisco by Saturday,” he said. “I won- der if I ought to send it by air mail. No,” he decided, “‘it will get there Friday night and be delivered on Saturday by ordinary mail.” And without another thought to the matter, he went on signing the remaining letters. Most of us are like that man. We take the mails for granted. When we address a letter to a place two days’ railway journey away, we mail it in entire con- fidence that it will be in the hands of the addressee at the end of the second day. Few, I am sure, realize that the trans- fer of a piece of mail matter from one part of the United States to another is a process quite as complicated and quite as wonderful as is the process by which a song sung in a broadcasting station on the Atlantic Coast is hurled through the ether to be reproduced by the radio receiver owned by a man in Colorado. Few, too, I am sure, suspect that this seemingly simple process of mail transfer is accomplished largely through the agency of a vast number of ingenious mechanical devices that have been developed for that sole purpose. And it is only by the invention of these time-saving and labor- saving devices that the Post Office Department has been able to keep abreast of the tremendous pressure of modern business and in- dustry. It permits no op- eration to be performed by human hands that can be performed more accurately, efficiently, and speedily by machinery. ] om in the office of a New York THE department main- POPULAR SCIENCE MONTHLY of improved practices and newly in- vented equipment. Congress encourages inventive genius within the postal service with a fund to provide cash rewards for employees who develop devices adopted by the department. As a result, some of the most valuable inventions that speed your letter to its destination have been developed by postal shop workers. Take the “facing table,’ for an example. - tains an Engineering Division that is charged with the responsibility of speeding the mails by means A Mechanical Sorter As letters are fed mechanically into this remarkable machine, the operator simply notes the address of each and presses a corresponding key ona keyboard. The machine then automatically carries the letters to their proper pigeonholes 43 The Inventors Who Speed YOUR MAIL Marvelous Time -Saving Machines Devised by U. S. Postal Employees By Norman C. McLoud Every hour collectors in the crowded business sections of our large cities dump into post offices thousands upon thou- sands of letters. These are addressed to every corner of the earth; they are in many sizes; in bundles and separate. The envelopes face in every possible direction. Some are upside down. Others are crosswise and askew. And this chaotic mass must be put in order. Each letter must be ¥ started on the way _ to its destination without chance of Unscrambling the Mail The “facing table’ is one of the most ingenious of the new time- saving postal inventions. Letters by the thousands are dumped on a circular platform where clerks turn them right side up, then insert them in a slot. They emerge neatly packed in stacks according to size, each letter face up with the stamp in the right-hand corner, all ready for the cancelling machine error. To do this by hand would require an army of clerks, and even then might result in utter confusion. But the facing table has solved the problem. This device consists of two round platforms, the upper fixed, the lower revolving. The clerks work on the upper platform, which resembles a large dining-room table with a slot at the edge.

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44 On this surface are dumped the letters. The clerks shuffle them about, turning them right side up, and drop them into the slot. The letters fall to the revolving platform, and are carried along to outlets at the far side of the table—long envelopes going into one channel, ordinary cor- respondence-size envelopes into another. They emerge neatly packed in stacks according to size, each letter face up and with the stamp in the upper right-hand corner, ready for the canceling machine. This facing table supplies an outstand- Pm ing example of the re ” spirit of codperation ae and loyalty that pervades the tech- nical arm of the postal service. The necessity for such a device had been recognized. Employees of the Mail Equipment Shops attacked the prob- lem and speedily produced the table. Without this table the canceling ma- chine, which in large post offices has super- seded the old-time practice of canceling stamps by hand, would be entirely use- less. A foreman in the Washington post office demonstrated this to me recently when he placed an armful of unsorted and unfaced dummy letters in the canceling machine. The envelopes emerged with the cancellation marks virtually every place on the letters except where they be- longed. HIS machine kandles the normal run of letters—envelopes of various sizes and shapes—at a rate of 10 a second. Gas and telephone bills, or other con- signments of mail matter of uniform size and shape, can be cancelled in this ma- chine at the amazing speed of a thousand a minute. However, these two machines do not solve the entire problem of getting the mail out on time. There still remains the highly difficult task of sorting the letters according to the destinations to which they are addressed. Virtually every collection in a big city brings in letters Cord Cutter J. D. Miller of the mail- equipment shops, operating the machine he invented for cutting 20 lengths of cord in one movement of a lever POPULAR SCIENCE MONTHLY directed to every state in the Union and every country in the civilized world. The established method of distributing outgoing mail has been by hand. Thus a clerk in the New York post office, for ex- ample, stands before a case containing about 60 pigeonholes, each marked with the name of some important city or geographical area, and tosses each letter into its proper niche. For years the postal authorities sought a better and more efficient way. Many machines invented for the purpose failed to solve the problem, until recently an Ohio manufacturing concern produced a device that literally can perform every operation of distributing mail except reading the addresses. I saw this machine—there is only one in use at present—in operation recently at the Washington post office. Letters are fed into the machine mechanically and pass in a steady stream before an operator seated at a keyboard resembling that of a linotype machine, except that the keys represent geographical areas instead of A Lock that Won’t Slip The problem of making a mailbag-cord lock that wouldn’t slip was solved by Thornton L. Richardson with the lever attachment shown below. This clamps the cord securely from above April, 1925 place. When the letter reaches th, pigeonhole for which it is intended it ia discharged into it. The pressing of the key sets a trigger on the container that ig released only by the mechanism con- nected with the proper pigeonhole. There are 120 of the latter, twice as many ag usually are contained in the cases used for hand distribution. This permits fine distinction in sorting and makes unneces. sary a second sorting. HESE inventions, of course, touch only one phase of the important operation of keeping the mails moving— handling incoming mail matter. Trang. porting the sorted mail to its destination is the next step. Here, too, the Pog Office Department has made generous use of the gifts of science and the products of inventive minds, both in speeding the mail and safeguarding it in transit. And speaking of safeguards, the En- gineering Division has called on science to aid it in supplying protection against bandits. Recently there was put into service a bandit-proof railway mail car, a veritable fortress on wheels, equipped with ingenious devices to protect it against attack. Its walls, roof, and floor are armored like the sides of a battleship, entirely bullet-proof. It is equipped with portholes through which Twine Holder An ingenious postal worker saved the government consider- able money by perfecting this holder that prevents loss of twine used in tying bundles of mail the letters of the alphabet. As the operator notes the address of a letter, he presses the ‘key that corresponds. The letter moves along in a container, and is picked up by one of a number of metal Cutter-Stamp ff A combination cord cutter and stamp. The blade is on the side shotguns may be poked to repel an assault. Around the barrel of each gun is a metal ball, which, when the weapon is thrust through the porthole, closes the latter tight, and per- mits the gun to be swung through a wide angle. In the portholes also may be placed magnesium candles, which will light the country for half a mile around and expose robbers to the bullets of marks- men within the car. Should a robber seek to escape the bright glare by diving beneath the ear, he is subject to a rain of bullets from shotguns that project through the floor. carriers on an endless chain. This conveyor carries the container over a series of pigeonholes, each a _ recep- tacle for mail for a particular Simple Spring Device Saves Fingers Before A. E. Wilde, a postal worker, invented this safety attachment for punch presses used in manufacturing mail- bags, 31 employees had lost fingers in the presses. His device —a spiral spring—has practically eliminated such accidents Ap Sl wes ko wo ot ao ot — 065 © I ~~ i in ded ee on A oe Oo

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» 1925 3 the » it ig Mf the hat is con- There hy as Used } finer N€Ces. touch rtant ing— ‘Tans- ation Post erous ducts g the 4 En- “ience yainst into car, a ipped ct it floor ship, ipped which repel varre] ball, m is thole, 1 per- wung ry be dles, y for Kpose arks- uld a right h the 1in of that floor. fety \ail- vice nts April, 1925 POPULAR SCIENCE MONTHLY A Terror to Bandits Surrounding the barrel of the gun used in the new armored mailcar is a metal Beneath the car are metal cones that ball. This closes the porthole tightly scatter bullets in all directions. when the gun barrel is thrust through Numbers of cars of this type prob- ably will be constructed in the near future. : Minor inventions issue from the Mail Equip- ment Shops almost daily. One of the most striking of these devices recently developed is a non-crush- able mailbag. The bag, light and wieldy, does not owe its durability to transverse bracing, as might be suspected. The secret lies in reinforcing it with a quarter-inch of “plymetal,”’ a newly in- vented material that ab- sorbs all weight and shock, distributing them through the length and breadth of the bag. O PROVE to me that the bag will supply protection to fra- gile articles in transit S. W. Farnsworth, Chief of the Engineering Division, placed several empty pasteboard shoe boxes in one, and then had a = 200-pound postal employee stand on it. to tackle the fastener problem. As the The boxes came out just as they had gone __— result, he invented a lever attachment in. Because the bags are flat and com- that clamps the cord lock from above, pact, many of them may be packed on engaging the cord lengthwise and holding one car, thus permitting pack- it secure under any conditions ages that ordinarily would of use. His device is now have to wait for the next train standard equipment, and he to go forward. has received his second cash The problem of devising an award of a few months, this effective fastening device for time for doing a thing that mailbags was one of the most **couldn’t be done.” troublesome that the technical J. D. Miller, of the Mail men of the Post Office De- Equipment Shops, recently partment ever faced. For evolved a simple machine that years, bags had been fastened in one motion cuts 20 lengths by a cord lock that slipped at of the cord required for fasten- annoying moments. Dozens ing mailbags. Another ingeni- of substitutes had been tried, ous employee saved the Post only to be discarded. Office Department a large sum A few months ago, however, of money by perfecting a Thornton L. Richardson of the holder that keeps in place and Mail Equipment Shops in prevents loss of the twine used Washington received a cash by carriers and clerks in tying award for devising a method bundles of mail. And a re- for bending tumbler springs cently devised combination for mailbag locks. The govern- canceling stamp and cord cut- ment’s recognition of this in- ter, to be used by post office vention inspired Richardson clerks in opening bundles, is a third clerk’s contribution to the movement of the mails. Sometimes there is an element of humor in these inventions by postal work- ers as, for example, when Tony Lombardi devised a “*jig’”’ whereby he doubled the amount of work he He Can’t Crush It To test the protective qual- ity of a newly developed fon-crushable mailbag, a 200-pound postal employee stood on the top of one of the bags containing just two empty shoe boxes. The boxes remained un- dented by the weight Repelling an Attack In the réle of robbers, a gang of postal clerks recently staged a realistic hold-up to test the effciency of the new bandit- proof railway mailcar. The photograph at the left shows them surrounding the car, while a riot gun barks from a porthole in its armor. Within the car a mail clerk, shielded by bullete proof steel, thrusts the muzzle of his gun through a porthole and sweeps the approaches. In the portholes also may be placed magnesium candles to light the surroundings and expose the : bandits to the bullets of the ms marksmen inside of the car %&,! ts BS we dl ae could do in operating a machine for reaming keyholes in mailbag locks. Tony kept his invention to himself, fearing he might be discharged for daring to make an unwarranted improvement on a gov- ernment machine. It was not until his superiors noticed how much more work he was turning out than any other man in the shop that his device came to light. Then, to Tony’s utter astonishment, he received a cash award, a citation from the Postmaster-General, and his “jig” was made standard equipment. NLY a short time ago, another cash award was made to A. E. Wilde of the Mail Equipment Shops, for a safety attachment for the punch presses used in the manufacture of mailbags. Before this attachment—a spiral spring that warns the operator of the drop of the punch —was installed, 31 employees had lost their fingers in the presses. Since the adoption of the device there have been few accidents in that department. Airplanes, motor-trucks, and even caterpillar tractors, are carrying the mails today to people in remote sections. For every letter and every package that is deposited in a mailbox must go forward to its destination without delay. That is the creed of the Post Office Department, and storms, ice, snow, and countless other agencies seem to conspire to prevent its being carried out. Against these op- posing forces the postal authorities have marshaled the powers of modern science.

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POPULAR SCIENCE MONTHLY April, 1925 New Milestones Passed How Problems of Flight Are Solved Aero-Skiing—A New Sport Skimming the ice at 90 miles an hour in a wingless airplane mounted on skis is a thrilling new sport devised by an inge. nious aviator of Quebec Province, Can, Preparing Balloons for Flight Ross Field, Arcadia, Calif., recently has become the scene of important developments in balloon navigation by army experts. At the right a balloon capable of soaring seven miles above the earth is being inflated preparatory to flight. Below, Lieut. C. P. Kane, com- mandant, is shown inspecting a balloon by means of a new movable balloon ladder ’ Huge Crankshaft Three men are needed * to lift the crankshaft of the world’s largest aircraft engine, the Napier “Cub,” com- pleted recently at Ac- ton, England. This motor weighs more than a ton and de- velops 1200 horse- power. A locomotive of the same power would weigh 75 tons SEAT A. Peas 2 > New Parachute A new type of airplane } : ° ° : parachute, worn like a Weighted Models Used in Airship Tests Seed, ie cendiet tant A novel test for lighter-than-air below. Aeronautical experts are in England. The re- craft was developed recently by able to determine from the behavior lease cord is attached army engineers at McCook Field, of the model exactly how the actual to the airplane, causing Dayton, Ohio. A model of the ship machine will react in the air to the parachute to open is suspended from a rack and filled the various strains and _ stresses automatically when with water. Then weights arehung to which a flight would submit it the wearer must jump

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3 a ge- April, 1925 POPULAR SCIENCE MONTHLY 47 in Aeronautics by Aviation Engineers The Los Angeles Moored to the Patoka Effecting a contact between a dirigible and a mooring ship is a difficult and complicated opera- tion. Here the Los Angeles is shown being hauled by cable toward the ship’s mooring-mast t RELEASE WIRE Plane- Catcher How England purposes to en- able the diri- gible R-101 to pick up _ air- planes in flight. Guided by a mirror, the pilot maneuvers his plane until a spring catch on the wing engages a special cable device lowered from the airship Above is seen the great dirigible Los Angeles under tow for the first time by U.S. S. Patoka, the only ship in the navy equipped with a mooring - mast. This test took place recently in Chesapeake Bay and, like pre- vious tests be- tween the Pa- toka and the Shenandoah, was entirely successful Artist’s conception of the RS-1, the first semi-rigid dirigible ever constructed in this country, now _scoutplanes and pick them upagain The Los Angeles remained moored for 45 minutes while the Patoka steamed up the bay. Then storm warnings caused the dirigi- ble to return to her hangar at Lakehurst, N. J. being assembled at Belleville, Il. ‘This ship will be able to launch

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Professor Moore’s home with air-purifying device on roof is shown above. A closer view (at right) shows the two funnels, one turned toward the wind. Air is forced through water in the large metal box : Air enters through unobtrusive ceiling registers. The amount of air admitted can be regulated by pulling the cords that can be seen above hanging from the register Actors Radio Play to Deaf NE hundred deaf persons, who could not have () heard a word without mechanical help, were guests recently at an unusual theater party in New York City. Installed in various parts of the theater was an adaptation of the public-address POPULAR SCIENCE MONTHLY .Weather Man Makes His Own Climate gs S CHIEF of the United States Weather A Bureau in Washington from 1895 to 1918, Prof. Willis Luther Moore studied weather and climate closely. He was especially interested in humidity. When he built a home in Pasadena, Calif., recently, he installed in it a unique system of ventilation. On his roof he built a water-cooling device for humidifying and purifying the air. A large intake funnel is faced to the wind by system that speakers r The system consisted of microphones on the stage to pick up | every sound, a vacuum-tube amplifier and 100 sets of head April, 1925 The inventor comparing the percentage of humidity of the air out of doors with that in- side the house i means of a weather-vane. Air from this funnel is forced through water and thence carried to all rooms of the house through ventilation pipes. A smaller funnel, which carries off the used air, is faced away from the wind. Each room has two ventilators in its ceiling. One admits the fresh air and the other takes off the impure air. In one test of the system Professor Moore found that with an _ outside humidity of 41 per cent the inside regis- tration was 74 per cent. The percentage can be regulated to suit the convenience of the dwellers, he says. The system is applicable to any climate. With proper furnace control and a means of regulating humidity, such as this system affords, ideal home climate is possible in any weather. Physicians agree that high relative humidity in the atmosphere of a home is of vital importance in preserving health. use when addressing huge crowds. A scene in the play heard by a deaf audience. The microphone is con- cealed. At right: Persons in the audience equipped with head phones phones for those more seriously deaf. The listeners, to whom a play had been nothing more than a “‘ movie” previously, reported that they heard every word. They are hopeful that the exper!- ment will open the doors of the theater to thousands to whom, until now, they have been closed. April, Pe ee er

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1925 from water of the 8. ae Tt the wind. rs in r and fessor itside regis- ntage tience em is oper lating fords, 1 any lative yme is ea)th. rowds. ick up | head hom a ported >xperi- whom,

POPULAR SCIENCE MONTHLY 49 April, 1925 Where the Big ‘Trees Crash Down The Mechanics of Lumbering—A Dramatic Story in Pictures

Largest Timber Raft Large-scale operations by which timber is being shorn from our forests are pic- tured here. The timber raft at the left is said to have been the largest ever constructed, containing more than 5,000,000,000 feet of logs. It was towed 1000 miles from the Columbia, Ore., to San Diego, Calif.

Starting for the Mill After the California big trees are A Raft 720 Feet Long felled, they are cut into mill lengths : for transportation to the This huge cradle raft of Douglas fir, shown a - under construction on the Columbia River game sawmill. This tree, which at Stella, Wash., is 720 feet long. The logs, held by the cradle, form an immense barge « the United States, according to recent estimates, have been reduced from 5,200,000,000,000 board feet to 2,200,000,000,000, or more than half

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The “Miss POPULAR SCIENCE MONTHLY April, 1995 ing Link” at Last? Discovery of ape-man’s skull may prove theory that Africa is the birthplace of man—New contributions to science tories, in countless shops, in the fields, forests, mines—even in the farthest corners of the earth—the work- ers of science are on the job every day for you. The volume of their achieve- ments in making your life more enjoyable and freer from the sufferings of want and I: THOUSANDS of research labora- disease is far beyond recording. Some of them remain forever unknown to fame. On these pages are simply a few of the month’s most important contributions to the world’s useful scientific knowledge. Ape-Man’s Skull Found ESCRIBED as the long sought “missing link,” a skull found re- cently at Taungs in South Africa, is con- sidered by some scientists as the most important anthropological discovery ever made. The skull is that of a creature with an intelligence rated between that of a man and an ape, filling in the important gap that so long has proved a stumbling- block in the explanation of evolution. Professor Raymond Dart, the noted Australian scientist, who found the skullin a limestone mine, has named the creature linking men with apes, ‘‘ Australopithecus Africanus.” The difference between men and ani- mals is associated with the size of certain Natural and Artificial Sunlight Combined in New Treatment The beneficial effect of ultra-violet rays, or artificial sunlight, in the prevention of disease, especially of rickets among children, has been demonstrated repeatedly by American and European scientists during the last year. Now the U.S. Bureau of Standards has determined by tests just completed that as a germ-killer the ultra- violet ray acts almost instantaneously. Bacteria of the kind found in sewage were killed in less than a second after exposure to the rays. graph shows Dr. Murray Levick, a British pioneer in the use of sunlight for healing, demonstrating his new apparatus for combining natural and artificial sun rays in the treatment of children. Note how reflectors are placed above the patient parts of the brain. The Pithecanthropus, the oldest man known, from the shape of a skull found, is judged to have been a creature who could speak. Judging again from the shape of its skull, Professor Dart says that the newly discovered manlike ape could not yet speak, but had a brain much more developed than that of an ape. The above photo- That is, the brain was enlarged in those parts associated with human characteristics. ‘ The skeleton remains consist of two fragments. One is a brain cast, which is complete and whole. The other is the face of the skull, which was found com- pletely embedded in the lime- stone of an old cavern. An interesting feature is that the discovery seems to support Darwin’s belief that Africa was probably the original home of the human family. male or female and was destined to remain so throughout life. Recently, though, Dr. Oscar Riddle of Carnegie Institution, Washington, D.C suggested that this belief in the unalten able fixity of sex is open to question, Some years ago a female pigeon in the Carnegie Institution’s laboratory gt Cold Spring Harbor, N. Y., de veloped a disease that caused the degeneration of its sex gland female birds having but one, This gland was on the left side of the pigeon’s body. In a shor time a male gland began to de velop on the right side of the bird and before long the pigeon actu. ally had turned into a male, Experiments performed by Doctor Riddle and others on other pigeons indicated that the sex of birds might be changed more o less readily. It was noted, more ewe rerey Sees Can Sex Change? CIENCE always has held that sex was a matter deter- mined at the very beginning of life by certain cell structures known as chromosomes; that long before birth the expected arrival was fated to be either Mammoth Flower Shows Amazing Growth Studying the amazing growth of this titanic flower, called “amorphophallus,” botanists recently discovered that it reaches the height of eight feet in a little more than a month. The plant is a native of Sumatra When the blossom is full blown it has an extremely un- pleasant smell. Its full magnificence lasts for only three days, when it collapses. The photograph is reproduced by courtesy of Mr. P. Dakkus, who 18 curator of the Botanical Gardens at Buitenzorg, Java over t right have | Docto sex of chang to be, degre of the Sup the di hangs perim Frank cago. forme has ¢: the c Ne cure: man far-r appl sorci gene 15 | app tion: tow nard

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1, 1935 t? led to dle, of D.C, nalter. in the Ty at eu de- sed the gland, t one, side of 1 short to de. he bird, n actu. d by mn other » Sex of nore or » MOre Baltimore, Md. ‘animals ‘tor Leonard and infections of the kidneys ~ April, 1925 ale glands developed on the were. much more than on the left. "Sprom these experiments sex changes have been brought about long after birth. Doctor Riddle suggests not only that the sex of an animal may not be the un- changeable thing it always was believed to be, but that, depending on the sex, the degree of sexuality is greater on one side of the body than on the other. Supporting this new suggestion that the difference between the sexes actually hangs on a most slender thread are ex- riments recently conducted by Prof. Frank R. Lillie at the University of Chi- cago. By a simple gland operation, per- formed on several hens when young, he has caused them to acquire virtually all the characteristics of male birds. New Antiseptic Stronger than Carbolic Acid BeepicaL men long have dreamed of discovering some universal anti- septic which, taken internally, would destroy all the disease germs in the body, providing virtually a panacea for human diseases. Now this dream seems closer to fulfilment with the recent development of a marvelous germicide, said to be 50 times more powerful than carbolic acid, yet so harmless that quantities of it may be swallowed without injury. The discoverer of the new antiseptic, called “hexylresorcinol,”’ is Dr. Veader Leonard, Chairman of the Clinical Com- mittee on Antiseptics of the National Research Council. He and his associates spent 10 years in developing it in the Johns Hopkins School of Hygiene and Public Health, In the experi- ments the antisep- tic was first fed to rabbits. When the suffered no ill effects, Doc- the six men work- ing with him took s Fe Nive fe it in increasing Ry a doses, and eventu- HORIZONTAL ally were con- FOOD CARRIER vinced that it was Pi ff 56 harmless. It was af tl al then that hexylresorcinol was successfully applied at Johns Hopkins Hos- pital for the treatment of patients suffering from and of the urinary tract. Insome cases, kidney in- fections of Jong standing were cleared up in 48 hours, according to the hospital records. The cures appeared to be per- manent, it was said. To determine just how far-reaching may be the application of hexylre- sorcinol to disease in general, a committee of 15 scientists has been appointed by the Na- tional Research Council towork with Doctor Leo- nard in further research. MIDDLE LAMELLA OR CEMENTING ‘SUBSTANCE WATER CARRIER _ POPULAR SCIENCE MONTHLY 51 Steel Tested by Flying Sparks from the Grindstone Photographs of s,arks flying from metal on a grindstone are employed in a new and exact method of testing steel invented by E. Pitois, a French aeronautical engineer. By this method, he claims, even the amateur can determine the degree of hardness and purity. Niagara’s Wasted Power WO and a half million horsepower are constantly going to waste at Niagara Falls, according to a report made re- SUMMER.WO0OD CELLS Secrets of Wood Disclosed by Microscope This remarkable diagram of the cell structure of a block of white pine wood, recently produced with the aid of a microscope, reveals that wood, instead of being relatively solid, is really composed of many tubular cells cemented together. The walls of the vertical cells, which are water carriers, form the bulk of the wood substance. horizontal cells that store and distribute food material. Spring wood cells that form during the early growing season, and summer wood cells produced toward the end of the season, together form one of the annual rings by which the age of the tree is told Running at right angles to them are Sparks are photographed on a black back- ground at very close range, and the images thus obtained are enlarged, revealing dis- tinguishing formations that are said to deter- mine the metal’s quality. The pictures show the new apparatus and spark photographs cently by Samuel S. Wyer, associate in mineral technology of the Smithsonian Institution. This represents 87,800 cubic feet of water, which flows over the falls every second and which might be diverted for power purposes, he states, without marring the scenic beauty of the falls. The total volume of water flowing over the American and Canadian Falls is 205,000 cubic feet a second, of which 94 per cent is carried by the Canadian side. At present 56,000 feet is diverted for water power and 11,200 cubic feet feeds the Chicago Drainage Canal, the Welland Ship Canal, and the New York State. Barge Canal. This leaves 137,800 cubic feet, of which, Mr. Wyer maintains, only 50,000 is needed for scenic beauty. The remainder, he states, may. be “‘harnessed.” Further water-power projects at Niag- ara Falls are impossible under the present treaty with Canada, which limits the amount of water that can be diverted for this purpose to 56,000 cubic feet, pro- ducing about 1,000,000 horsepower. The Work Your Eyes Do M?2st of us realize the importance of good eyesight; few, though, prob- ably know to what extent we employ our vision in our daily work. In a recent test conducted by a commercial concern study- ing problems in illumination it was deter- mined that the ordinary run of indoor workers—clerks, machinists, printers and the like—use their eyes 70 per cent of the time they are at work. Among 20 occupations that may be classed as “close work” it was found that in only six did the necessity for close visual application fall below 50 per cent of the working day. The object of this eyesight test was to determine how much the production of workers may be increased by better illumination without placing an undue tax on their eyes.

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52 Livermore, Calif. In order to do away with unsightly rows of individual mailboxes set on posts at crossroads, groups of farmers in many communities fix their mailboxes to large discarded wagon wheels set on the ends The newly invented metal stand serves the same purpose and helps to keep the highway more attractive. The sides of the device can be used for posting small local notices. Mounted at the top of the center post on which the supporting frame revolves is a small road sign in the form of an arrow. of fence posts. Rural Mattox Stand Revolves A REVOLVING metal stand, holding from two to 12 mailboxes, saves space and time for the postman delivering rural mail near POPULAR SCIENCE MONTHLY April, 1925 ‘Ten New Inventions for . Pocket Check Protector A The protector perforates check and fills holes with ink CHECK protector, small enough to be carried in the vest pocket, is a recent j vention for the convenience of business a who are careful to prevent raising of thei checks. the cipher, and the dollar sign. There is an ink pad between the lower and upper plates, When a check is inserted and the protector pressed, fine sharp pins prick holes in the check and these are filled with fluid from the pad Any erasure on this inked number can be de. tected easily. cially designed figures can be used on the device, It includes all‘ the numbers needed For additional protection Spe- 4 = + + eS é ' Ww Inflated Safety Belt for Bathers Fits Tightly J BRIGHING little more than a pound, this inflated safety belt for bathers fits over the shoulders and straps securely around the body. It has four large air chambers, two in front and two in back, with vulcanized seams. Once adjusted, it cannot come loose, the manufacturers claim, and it interferes in no way with the movements of the bather. An air valve controls the inflation. AN ELECTRICAL process for manufactur- ing carbon black, a pigment widely used for such purposes as printer’s ink and car- bon paper, recently has been devised by the U. S. Bureau of Mines. The present process uses natural gas. This Novel Fire Alarm Rings the Door-Bell NE of the latest fire-alarm devices is connected with the electric door-bell circuit of a house, so that if a fire starts, it sends out a warning by ringing the bell. In the photograph below the alarm is being tested with a lighted cigarette. Within from 30 to 60 seconds after the heat is applied, the inventor claims it will start the door-bell ringing. * * * * * , » * > A cigarette sets off the fire alarm New Voltage Tester Tells the Kind of Current O TELL whether an electric current is alternating or direct, as well as to measure its voltage, this new type of voltage tester has been designed. It does not require the use of ‘lamps and will measure up to 550 volts. The Testing voltage from a light socket apparatus is inclosed in a rugged fiber housing. A magnet coil operates a plunger against the tension of a spiral spring. The position of this plunger on a scale indicates the voltage. Pointed hooks in fiber-insulated handles at the end of long wires make it easy to get the lead wires into the circuit. The photograph shows the device be- ing used to test the current from an ordi- nary electric-light socket. illeg

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ctor eck ad, spe- rice, lis rrent as to e of se of asure The fiber unger pring. scale oks in April, 1925 Our Every-Day Use Typewriters Silenced YPEWRITERS fastened to desks with newly T invented shock-absorbing attachments are said to become practically noiseless and rattle-proof, thus saving wear on the machine as well as on the nerves of office workers. The rubber feet of the typewriter fit into sockets of the attachments, where they rest on felt-covered coilsprings. The machine is held firmly by auto- matic hooks that engage the frame as the legs are inserted in the sockets, and is released simply by pressing back the hooks. Parts underneath the machine remain accessible for cleaning or repairs. POPULAR SCIENCE MONTHLY A Push Opens New Typewriter Desk A SLIGHT push brings the platform of this new typewriter desk into position. The lid is raised halfway before the typewriter platform moves, then a straight push backward brings the typewriter into place, making the operation easier and simpler, it is claimed, than that of the ordinary drop-head typewriter desk. The platform locks automatically into position. Rigid supports prevent the platform from shaking, and ample knee How the typewriter legs rest on four shock absorbers room is provided for the operator, whether the desk is open or closed. Special Pen Marks Packing Cases with Ink DDRESSES and marks made with crayon or pencil on packing cases and bales often rub off so that they are illegible. Much more permanent marks may be put on with ink, it is claimed, with a special pen in- vented recently for that purpose. The marking pen is held upright The flow of ink depends upon the pres- sure on the rubber nib. Any good ink may be used. The writer uses it like an ordinary pen, but holds it a little straighter. The pen can be used, also, for writing display cards or window signs. A JOURNEYMAN baker in Paris, France, claims to have discovered a formula for bread dough that will keep the loaves in edible condition for months, or even for years. MAKING synthetic rubber has resulted recently in the discovery of a synthetic chemical substitute for cocaine. Tuto- kain, the new compound, is made from the intermediate products. It is said to be effective as a local anesthetic. Self-Feeding Brush Aids in Cleaning Type O DO away with the rather mussy method of cleaning typewriter type with brush and pin, a self-feeding type- writer brush has been designed. It con- sists of a hollow metal handle containing type-cleaning fluid, which is fed into an adjustable bristle brush. The fluid is applied by pressing a pump button. for House Doors ‘THs ingenious door lock works like the combination of a safe. The key is inserted permanently in the lock, which has a set of buttons around its outer edge. It can be turned only when the proper set of buttons has been depressed. To bring the buttons back to their original position, the key is pulled outward after the door is opened, and the lock is A typewriter brush shaped like a pencil again ready for service.

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POPULAR SCIENCE MONTHLY

April, 1925 Curious, Useful and

Caterpillar Tractor and Plow Combined One of the most compact farm implements exhibited at a recent German motor show was this tank-plow, said to be the first machine to combine caterpillar tractor and plow in one unit

© U.&U,

These Wheels Have Run Nearly a Century For nearly a century these clock wheels have been keeping good time. The clock was built in 1828 by Isaiah Quimby Lukens, and for nearly 50 years recorded time in Inde- pendence Hall, Philadelphia. It was remounted recently in the attractive new town hall at Germantown, Pa,

Mammoth Dynamos for Russia There is room for a fair-sized switch engine within the stator of one of the huge generators comprising a new power plant that is to sup- ply the city of Leningrad, Russia, with light and power. Four of these immense dynamos, each of 11,000 volts, already have been deliv- ered by the Swedish General Electric Company

: ci oe? x : t } \ ) Buss sii tees 4ittet heeey be af oR al pr agde f

Like a Huge Mosquito A remarkable new machine for dig- ging post holes can bore a hole three feet deep and nine inches in diameter in 30 seconds. A pull on a lever is sufficient to start the drill downward. An- other pull stops it at the desired depth and brings it back to the starting point. The inventor, Otto Coil, of Washington Court House, Ohio, built his original model from 23 pieces of farm machinery

A Machine that ‘*Thinks”’ If you ever have tried to score an automobile race, you will appre- ciate the complexity of a new machine that keeps an_ accurate printed record of each speeding car and sup- plies a complete analysis of the contest <—«

Va Th hot pli stre mo rec

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POPULAR SCIENCE MONTHLY April, 1925 Ingenious Machines a . a brick plants, and road construc- Mee agaitiity < . i we tion jobs, an economical gasoline 200 Aboard y a ee 2 locomotive—a tractor on rails— ee ' has been perfected. It consumes Just _ to demonstrate , eee oe b about five gallons of gasoline a day the immense propor- ‘ . tions of a powerful new type of mountain locomotive, 200 men recently climbed aboard. More than 150 locomotives of this type are in use on a Pacific Coast railway

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yee OMEN vi 56 POPULAR SCIENCE MONTHLY Electric Handsaw Has Many Uses A carpenter using the electric saw on the job A NEW combination plier and wrench de- signed for many uses, can grip anything, from:a cotter-pin to a nut on a three- quarter-inch bolt. A NEW portable elec- tric circular saw en- ables workmen todo power sawing on the job with speed and accuracy. It is said to cut satisfactorily wood, wallboard, plaster board, fiber, linoleum, hard rubber, insulated cables, brass, and many other materials. It can be used also in the packing indus- try for cutting meat. Since the body of the saw is of aluminum the tool is light in weight and easy to handle. It has a cutting capacity of two inches in hard wood and has attachments to be used for beveling or other similar purposes. The air-cooled motor is placed directly back of the saw. This runs only while the operator holds his finger on a contact trigger switch in the handle of the tool. A guidein front of the saw enables it to cut on the line straight and clean, elim- inating costly trimming operations. The tool can be run from a wall socket. New Polishing Tool Has Inflated Wheel A PNEUMATIC wheel for grinding, buffing, and polishing, designed to speed up work along these lines, has just been put on the market. The wheel is in- flated by means of a valve, just as an auto tire is inflated. The grinding surface is removable. Sandpaper, emery, or any other abra- sive surface can be attached to suit the convenience of the user. The grinding strips are held by a flange. The operator pushes the teol along the surface of the work exactly as a plane is manipulated, the wheel being motor- driven. The abrasive surface is at- tached around the circumfer- ence of the wheel, which is inflated April, 1925 Handy Pocket Screwdriver Has Folding Blades eet to a knife, a man finds himself more often in need of a screwdriver probably, than of any other tool useq lor ordinary purposes. A Michigan manufacturer re- cently has de- veloped a fold- ing screwdriver that can be car- ried in the pocket with one’s knife. Three blades of different sizes lock open separ- ately, giving the compact tool a wide range of usefulness. When the blades are not in use, they are locked tight in the handle. Finds Way to Store Surplus Steam for Future Use A SIMPLE device that enables sun plus steam produced during slack hours to be stored in a reservoir until the time of peak load brings a need for it, has ; been devised by a Swedish engineer, Dr Johannes Ruths. In recognition of his valuable invention, the Swedish Academy of Engineering Science awarded the inventor a gold medal. The steam accumulator is a_ large cylindrical tank with spherical ends, filled with water to 90 or 95 per cent of its capacity. Steam not needed at the moment for the engines is passed into the remaining space, where under the pressure it condenses to superheated water. Later, when more steam is needed than the boilers can supply, the water level in the tank is lowered, decreasing the pressure, and releasing the steam. Loss of temper- ature is prevented by a heat-insulating wall built about the tank. Automatic Machine Saves Time and: Labor in Truck Loading i only one man is needed to drive a delivery truck when heavy merchandise is carried, an additional man is required to load or unload it. Double expense therefore is incurred on trucking jobs, merely for the few minutes when loading or unloading is done. For some time manufacturers have been looking for a mechanical aid, so that material could be lifted into truck bodies by the driver. A German engineer recently invented the automatic truck loader for barrels shown in the photograph. With this, it is said, one man easily can do the work of unloading or loading. The device consists of a V-shaped tilting platform that slides up and down an inclined track lowered from the rear of the truck. This platform, or carrier, is operated bya hand winch on the side of the truck. When a barrel is to be unloaded, it is rolled from the floor of the truck to the platform. Lowered to the bottom of the incline, the platform encounters a stop that automatically tilts it in such a way as to discharge the barrel to the ground. In loading, the operation is reversed, the barrel being rolled on the platform from the ground and pulled up the incline. While the larger photograph shows two men at work unloading barrels from a truck, it is quite apparent that the deviee would enable one man to handle the heaviest loads unaided. “LULLEPYYVTTTT iu TV 1 ett eae ui e a Asi vin ee F cw heavy barrels are discharged from & ~ truck. The view at ~ the left shows a barrel © being rolled on the — platform, which is lowered down the in- clined track. At the bottom (above) the platform is tilted, thus discharging the load ee re for m tion ¢ names the sa tion is The on as} which rotate positic For hand | highes fixed autom dies. adapti OR po “‘pulliz used | Opera‘

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er aself iver, 1 for - SUI. lack ‘il the , t, has r, Dr, ntion, eering - gold large ends, ent of at the to the essure Later, in the in the pssure, ~mper- lating rom & deviee le the 4 4 & 4 bd - April, 1925 New Radio Wrench Spins Round Nuts Tightly NE of the chief sources of trouble for the man who builds his own radio set lies in loosened connections. Small, d nuts in almost inaccessible places are particularly difficult to tighten suffi- ciently to insure good, permanent contacts. The newly de- signed wrench shown in the il- lustration has sharp teeth tapered so as to grip knurled round nuts firmly, with but slight pressure. The long reach of the shank makes the tool especially useful, and the handle gives strong leverage. The shank is tooled from one piece of steel and hardened fcr constant service. Numbers Cylindrical Parts Automatically ppreetic numbering of cylindrical metal parts has been made available for machine-shops by the recent inven- tion of a machine that also will stamp names and trade marks on the work at the same time that the numbering opera- tion is performed. The parts to be numbered are carried on a special holding fixture on the table to which: the device is attached, and are rotated automatically into the correct position. For ordinary changing of the numbers a hand lever is depressed to give the next highest number. The lever strikes a fixed point on the holding fixture, and automatically advances the numbering dies. This arrangement makes the device adaptable for serial numbering. POPULAR SCIENCE MONTHLY 57 Railway Ties Dated with a Brand BRANDING outfit to mark railway ties is a new aid in keeping railway tracks in good condition. Railway companies usually keep records of the year in which ties are laid by mark- ing them with special nails. These are inspected at in- tervals, and the oldest ties replaced by new ones. The nails, however, often are knocked off and the record destroyed. The new branding device burns into the ties the date on which they are laid. It consists of a metal plate with raised numerals indi- cating the month, day, and year in which the branding is done. This plate is at- tached to a handle and is heated by a small torch. It can be used also to brand tools and other equipment. Gasoline is the fuel used in the small torch, which will operate from 11% to four hours, depending upon the use to which it is put. With special at- tachments, the torch can be used for heating a soldering iron or for a blowtorch. How the tool brands the date on a wooden surface AN IMPORTANT advance in standardiza- tion has just been made in the adoption of standard screw threads by the Ameri- can Engineering Standards Committee. Simple Rack Keeps Paint Brushes Pliable T IS a well known fact that paint brushes will last twice as long if they are properly cared for. To assist the professional painter, as well as the home worker, in keeping brushes in good work- ing condition, the simple rack pictured at the left recently has been invented. It accommodates brushes of almost any size, suspending them in water or what- ever other liquid is used to keep the brushes soft and pliable. The rack rests on the container, no matter what its size or shape, and forms a series of slots in which the brush handles are held. With Powerful New Jack One Man Pulls a Steel Railway Car frok pulling and hoisting work, a powerful little machine called a “pulling-jack,” recently invented, can be used in an amazing number of ways. Operated by one man, it is said to be proving a great labor-saver, especially in house-wrecking and on railways. It is declared to be capable of moving anything weighing up to 100 tons. With One man pulls a railway car with the aid of the jack the jack one man can pull down a whole brick pier, a wall, or chimney, ordinarily the work of many men. In the photo- graph the jack is being used to pull a de- railed steel railway car back on the rails. For stump-pulling and moving heavy machinery it is said by the manu- facturers to be very efficient. The machine combines the principles of the lifting jack and winch. A pawl- and-ratchet mechanism is used to wind a cable on a drum. The jack can be oper- ated at six different speeds. Cleans the High Lights in Shops and Offices ¢ ay FACILITATE the cleaning of elec- trie-light fixtures and_ reflectors located far from the floor, a new brush mechanism attached to a long handle re- cently has been perfected. A lever at the side of the handle holds the brushes against the surface to be cleaned, and a hand crank revolves the brushes.

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POPULAR SCIENCE MONTHLY 4 hee TAD PE ee Demonstrating a model of the proposed high speed monorail subway. April, i995 Monorail Subway Proposed in — England The inventor model of his Be car. It is held ups on the single rajj guide wheels ahem roof of the gap Emerging from the station the car dips down into a deep tube i ee ss oe a . A HIGH-SPEED underground railway by deep tubes in or = system in which cars running on a which the ears — eee ae single rail could travel at the rate of 60 would run on a ee: miles an hour, is the latest suggestion offered in England to solve the transit problems of large cities. A demonstration was given recently by means of working models by the inventor. The proposed system would consist of stations just below the surface, connected ‘ single ground rail. They would be held upright by guide wheels running on a guide rail above. The wavelike course of the railway, the inventor believes, would serve to quicken the speed of the trains on departure and to retard them at the “ny approaches to a station. For maximum speed, as well as comfort, the inventor has designed special streamlined cars. Odd River Ferryboat Driven by Tractors had SPITE of old rivermen’s prophecies that it couldn’t be done, two Fordson tractors recently began operating a ferry on regular schedule on the Tennessee River at Paducah, Ky. Engineers who have examined the novel boat declare the power to be an improvement over steam for this purpose. The tractors are placed lengthwise with the boat, about six feet apart and are coupled together. The Ae Sl), se Ards wee i= World’s Greatest Tunnel HE greatest tunnel in the world soon will be built under the Mersey River in England to link the city of Liverpool with Birkenhead and adjacent towns on } the south bank of the river. It will have an internal diameter of 44 feet, greater than the Hudson River tunnel now under | construction. The tube will contain two decks, one bee for automobiles, the other for streetcars. tractor shaft and paddle wheel are con- nected by chains and sprockets. By means of a special device the pilot can shift gears from his cabin. After the tractor en- gines have been started, the pilot has full control over them, stopping them in neu- tral, reversing, or shifting to low and intermediate gears. One tractor can run without the other or both can be made to pull together. The boat can be run as easily as an automobile, it is claimed, thus doing away with the need of licensed engineer and pilot. How the two tractors are geared to the stern paddle wheel. They are controlled from the pilot’s cabin Novel Test Shows Strength of Bridge Railing AFTER an accident in which part of the concrete balustrade of a bridge at Springfield, Mass., was knocked down, engineeis made unique tests to determine its exact strength. They used levers con- sisting of wooden planks inclined at an angle, butted against the base of the rail- ing. Ropes tied to the planks were at- tached to the top of the railing by means of hooks. Sand was poured into weight boxes on the ends of the planks. The amount in these boxes when the railing fell deter- mined the weight necessary to overtum the railing. Although the railing fell in- ward instead of into the river in the tests, the results were taken as holding for either direction. The tests served to establish standards of strength for future bridge construction. The novel tractor-driven ferryboat docked at Paducah, Ky., on the Tennessee River. at n nent sear pow whi ligh of s ligh will senc mile in if in tl ing Pro’ fuse hea;

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aximum inventor cars. ength part of a bridge d. down, etermine yers con- 1d at an the rail- were at- Yy means boxes on nount in ll deter- overturn y fell in- she tests, ding for tandards truction. Niagara to Be Illuminated Ts spectacularly beautiful effect, the illumination of Niagara Falls at night with searchlights, will be perma- nent after May 24. Twenty-four powerful searchlights, casting 1 1/3 billion candle- power, will be dedicated on that date, which is Queen Victoria’s birthday. Eighteen years ago the falls were lighted for 30 days, attracting thousands of spectators. The above photograph was taken at that time. In the new lighting of the falls, more powerful lights will be used, color screens and light drills sending beams that will be seen for 75 miles around. A Ship without a Rivet N OIL-TANKER in one piece, with- out a rivet in its hull plates or a bolt in its steel frame, the first one ever built in the United States by the electric weld- ing method, was launched recently in Providence, R. I. Terrific heat generated by electricity fused together the sheets of steel and heavy angle iron in the tanker’s frame. POPULAR SCIENCE MONTHLY “This photograph shows the spectacular illumination of Niagara Falls in 1907, which will be eclipsed by a more powerful system of searchlights ee Se : | ( N, * KLAHOMA |. 6 TAR KANSAS t ° — (ILLINOIS jyNDIANA; a ve | nTrucKkyY / _ eee f 5 COMPLETED eammamaae PROJECTED axe N\ = = \3 a) \ > bund N Projected chain of natural waterways along the eastern coast from Boston to Mexico The remarkable one-piece welded boat just before launching at Providence, R. I. U. S. Plans to Link Chain of Coastal Waterways Y LINKING a long chain of natural waterways with canals a continuous channel eventually will be available along the entire eastern coast of the United States, from Boston to the Mexi- can boundary on the Gulf of Mexico. By far the greater part of this route is now open for boats of limited draft. The en- tire route has been surveyed by U.S. Government engineers. It is possible today to make the entire trip from Massachusetts to Florida with small craft without once going to sea. The great system of canals that ex- tends from New England to Florida is known collectively as the Atlantic. Inter- coastal Waterway. When the work now in progress is complete, it will afford a continuous channel 12 feet in depth as far south as Beaufort, N. C.

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POPULAR SCIENCE MONTHLY rein Interesting Giants Do You Know of Any Bette i ia aaa id The World’s Smallest Fountain Pen This loaf of bread, said to 5 : : ‘ ’ The midget fountain pen will hold a drop of ink and be the largest ever baked write 300 words, while the large one will hold 120 in one piece, is 60 feet : : : = : ; long and contains more and write 36,000 words. ‘They are shown side by side than 400 pounds of flour. It was turned out recently in Minneapolis. Bakers here are seen removing the huge loaf from the oven Sixty-Foot Loaf _ Huge New Dam In the Kentucky hills near the town of Burgin, engineers are constructing what is said to be the world’s largest rock-filled dam. When completed it is expected to develop 36,000 horsepower, 13,000 more than the great Roose- velt Dam in Arizona a a * Pheteteta ee & Rs dpteienedihad Hegs fH Twenty-Foot Rule The makers of this enormous slide rule say it is the world’s largest. It is 20 feet long when extended, and 10 feet long when closed. Compare it with the ordinary foot-rule that 1% held in the child’s right hand Rolling Door Weighs Two Tons This two-ton rolling steel door, said to be the largest made, was installed recently in a Brooklyn, N. Y., factory at a switching entrance 45 feet wide and 17 feet high. It is operated by an electric motor, which is shown at right April,

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» 1925 tS ter ; slide st. It and 10 are it hat is hand

April, 1925 and Unusual Midégets Claims to Records than These?

Inch-High Electric Motor POPULAR SCIENCE MONTHLY

The Largest Rock Ever Quarried From the Stone Mountain Quarry at Atlanta, Ga., was taken recently what is believed to be the largest solid rock ever quarried. It is 40 feet high and contains 100,000 cubic feet of granite. Compare it with the man

The tiniest motor, made by H. McBroom of Houston, Tex., is less than an inch high and weighs only a quarter of an ounce

A Book with 4000 Pages Containing 4000 pages, this Chamber of Com- merce registry book is said to be the bulkiest volume in the world. It weighs 340 pounds Two hundred and three tons of steel make up this giant locomotive recently designed by a Delaware & Hudson Railway engineer. It is said to develop one-

— irs 8 e we ‘ae ee

|) < Cc - ae /

Railway Giant third more power on one-third less fuel than any pre- vious locomotive

LUE —

Midget among Airships The world’s smallest semi-rigid dirig- ible, the MR, was completed in Romea few weeks ago from designs by Lieut.- Col. Umberto Nobile. This little air- ship is only 105 feet long, as compared with the 663-foot length of the dirigible Los Angeles. It is designed to de- velop a speed of about 40 miles an hour A Knife with 75 Blades Some of the smallest blades ever made are contained in a marvelously carved knife produced by William Bamforth, member of a cutlery firm in Sheffield, England. The knife contains 75 blades, many of them ornamented with designs that are considered among the most perfect ever worked in steel

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An automobile me- chanic driving rivets in a brake lining with the aid of the new machine. Pressure increases automatic- ally as the rivet is set New Rivdting Machine Aids in Relining Brakes ie RELINING brakes, rivets must be made absoltely tight, else the brake bands will “ns break loose on account of chafing actiqa on the rivets. A machine for driving rivets, recently put on the market, is said yo do especially good work on account of ;its toggle action, which gives it increased leverage. It is operated by a pedal. . At the beginigng of the riveting opera- tion comparatiWyly light pressure is ex- erted, the pressiye increasing automatic- ally as the rive+ is set. Small or large brake bands cay; be riveted either from the top or bottom. Eight dies and punches are fur:,jshed with the machine. Bumper and Emergency Winck Combined or. the main highways, on bad coun- try roads, the automobile driver often has to depend entirely upon his own efforts to get himself out of trouble. When stuck in mud or sand, the combination bumper and winch shown in the photo- graph at the right would prove a welcome aid. Attaching the line to a near-by tree or telephone pole, a man without other assistance could pull his car out on to firmer ground. The winch isso geared that 100 pounds of power on thd hand lever by which it is operated produces 5000 pounds on the line. Small springs prevent rattling in the bumper. BY HEATING heavy and vegetable oils by electricity, a Russian inventor, M. Ma- khonine, recently perfected for the French army what he claims to be a cheap and efficient motor fuel. 4 é POPULAR SCIENCE MONTHLY April, 1925 Toolbox Forms a Convenient Step METAL box that slides under the runningboard, providing a convenient place to keep tools, is automatically locked so that its con- vents are safe from theft. An added feature, appealing especially to women, is an auxiliary step that comes into position when the toolbox is open, making it easier to get into the car. When the door of the car is opened, a plunger in the door jam is released, so that the auxiliary step drops into place, at the same time making the toolbox accessible. THE world spent $3,360,000,000 for new motor ve- hicles in 1924, a survey by the U.S. Department of Commerce shows. On January 1 of this year there were in operation in all countries 18,615,000 passen- ger cars, 2,892,000 trucks and 1,262,- 000 motorcycles. When the door of the car is opened, the front of the toolbox compart- ment automatically drops down to form the auxiliary step shown above. Left: The toolbox opened Gompresses- Air Pistol Cleans Parts Quickly PERATED by means of compressed air, this spraying gun is designed particularly for cleaning automobile en- gines, transmissions and gears. Either gasoline or kerosene may be used. The spray is controlled by a trigger, and the gun is gripped and held like a pistol. The device may be used, also, for ap- plying wood preservatives, insecticides, creosote, thin paint, or whitewash. THE streets of Paris, France, now are swarming with miniature one-passenger taxis, compact and light, and exceedingly whe sineed P * ‘a economical in tires, gasoline consumption, sie 4k Ge Me ae Ak dh ance. and cost of manufacture. They have a which is operated by compressed air wheel track of only 46 inches. 1H ene (° i peseapana The ingenious combination bumper and hand winch. The picture shows a driver pulling out the iron lever by which the powerful winch is operated. The line can be attached to a near-by tree or a telephone pole Ap’ del; cor car del: doy floc anc to 1 TH gar Toa sib! por

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ly ressed signed le en- Rither The id the ee or ap- icides, w are senger dingly :ption, lave a April, 1925 Ge gee ene? i. ee” This Auto Can Be Turned into a Delivery Truck A QUICK change from a comfortable and roomy pleasure car to a small delivery truck has been made possible by a newly devised automobile body with convertible seats. When it is to be used for pleasure, the car is provided with upholstered rear seats. When it is to be converted into a delivery truck, these seats are taken down and reversed to form a smooth, even floor. The rear of the body is on hinges and swings downward to provide access to the truck from the rear. THE state of Massachusetts recently be- gan consideration of a plan to utilize the roadbeds of abandoned railways as pos- sible highways for motor-truck trans- portation routes. Cars for Business or Pleasure POPULAR SCIENCE MONTHLY Either one of these two types of convertible bodies enables the owner to trans- form his pleasure’ car quickly into a small truck Driven by an electric motor, this testing machine turns the wheel against the brake, Flexible Traffic Post CIENCE and man’s inventive genius are continually trying to care for the careless motorist. One of the resultant products is a portable flexible “iron man” as a traffic guide for street crossings. The invention is designed especially for subur- ban and rural districts where stationary concrete or metal traffic posts very often are a menace, especially at night-time. When a car strikes this signal post, no damage is done, for the upright shaft is mounted on a heavy but flexible spring. This allows the signa! to bend down out of the way so that the car may pass over it harmlessly. The upper half is made of tube steel and is half an inch larger than the sup- porting spring. When a care- less motorist tubs or knocks against the sig- nal, the tube striking against Takes Hard Knocks the spring rings so that it may be heard two blocks away. Redlights may be at- tached to the post. Snow, ice, and inclement weather are said not to affect the operation of the new signal de- vice. This new portable traffic post is mounted on a flexible spring so that if struck by acar, it will bend, as shown above, preventing damage to both the car and the post Convertible Body Useful for the Farmer ANOTHER new type of convertible body for Ford cars is especially de- signed for farmers and merchants who use their machines for both pleasure and business. This body is so designed that the rear seats fold forward into the floor and out of the way. A tail gate can be lowered from the rear. When the tail gate is closed, there is nothing to distinguish the machine from other pleasure cars of the same make. The manufacturers claim that it can be converted from pleasure to business car in less than a minute. Auto Brakes Now Tested by Machinery T° often the adjustment of automo- bile brakes has been done by ap- proximation and guessing. By means of an ingenious dynamic brake tester re- cently invented, one can tell exactly how many pounds of pressure there is on a brake drum while the wheel is in motion, and make adjustments accurately. Only one man is required to make the test with this machine. After jacking the car off the floor, he sets the brake pedal with a special depresser that holds the foot or service brake under a constant pressure. The brake tester, driven by a motor, is then clamped firmly to the automobile wheel. An electric motor turns the wheel against resistance of the brake, and an indicator on the machine records the num- ber of pounds pressure at all points on the brake drum. Adjustments can be made while the brake tester is on the wheel. In case of four-wheel brakes, the front wheels usually are given two-thirds of the pressure applied to the rear wheels. Plan Revolving Garage A POSSIBLE solution of the shortage of parking and garage accommoda- tions is offered in a revolving garage to be erected soon in the West End of London, England. The floors of the garage will be ar- ranged as concentric rings, each of which will be divided into a number of one-car compartments. The floor will be revolved so that any compartment can be brought into line with the main entrance.

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POPULAR SCIENCE MONTHLY Dressing-Rooms for Taxi Drivers KK SEXING clean and well groomed is a business matter. This is the belief of a Chicago taxicab company that re- cently installed dressing-rooms for its drivers in several garages. These rooms are equipped with the most modern con- veniences for bathing, shaving, grooming, and even for polishing shoes. No one appears more constantly be- fore the public than a taxicab driver, and upon his appearance, the company be- lieves, depends largely the publiec’s afti- tude toward his

employers. With a good appearance comes a bearing of self respect.

A FRENCH in- ventor, De Grammont de Guiche,has per- fected a method that enables an airplane pilot to tell by sound his exact flying speed.

It Pays Them to Look Fit Each taxi driver is provided with an individual dressing room, fitted with porcelain washba- sin, shaving mirror, and toilet acces- sories, as shown above. Here he keeps himself well groomed for the day’s job. In ad- dition, the most modern bath and toilet facilities are at his service

Heavy Moving Simplified by Low-Slung Van HE heavy job of lifting large packing cases and articles of furniture in loading or unloading a motor-van has been made much easier and simpler, it is claimed, by the recent development of a new type of truck with extremely low chassis and body. The floor of the moving-truck is hardly above the knees of the average sized man, thus greatly reducing the lifting distance for the furniture remover or the ex- pressman. The low center of gravity also is said to assure greater safety in turning corners with a heavy load, and better riding qualities over rough roads. The new design, known as the low drop-frame chassis type, is the invention of a California truck manufacturer. A striking comparison with the ordinary type of motor-van is shown in the

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accompanying il- lustration. BY CAUSING suc- cessive waves of sound to interfere with each other’s transmission, Dr. G. W. Stewart, a professor of phy- sies at the Univer- sity of Iowa, has perfected a device that he believes in time may be used to eliminate unde- sirable noises and to adjust sounds to suit the taste ake and the nerves of

The new low-frame motor-van (left) compared with an ordinary van any individual.

Simple Wire Brush Keeps Carpet-Sweepers Clean TRONG bent wires in this newly jp. vented brush quickly remove tangled hair and thread from the brushes of carpet-sweepers or from vacuum cleaners, Thus a common annoyance to the house. wife has been removed by a simple but effective invention.

Electrical Blower Cleans Dust from Machinery PERATING either as a suction cleaner or blower, an ingenious new electrical aid for the mechanic removes coal dust, dirt, and other accumulations from machinery. <A _ hose attachment enables the operator to get at all parts ofa large machine or switchboard and elimi- nate all dust. The cleaner can be attached to any light socket. In the photograph the de vice is shown being used as a blower, When used as a suction cleaner, a dust bag is attached. The apparatus can be slung over the shoulder of the operator with a strap, leaving both his hands free for work. When operated as a blower, the air leaves the nozzle at a velocity of 200 feet a second—nearly 140 miles an hour. Cleaning machinery with electric blower

Sugar Made from Weeds EVULOSE, a valuable sugar that heretofore has cost from $30 to $110 a pound, can now be made cheaply enough for table use by a process perfected by the U. S. Bureau of Standards. It 1s ex tracted from dahlias and from Jerusalem artichoke, a common weed.

Thi B” a ats with and t unde! Ne ye s mach time over laced from only menc¢ repai garas of be fan b direc belt embe surfa nati Dar plu illu

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uction 1S new Moves lations hment rts of a elimi- tO any she: de- slower. a dust can be perator ds free he air 00 feet our. lower eeds ir that to $110 r enough cted by It is ex- rusalem This New Floor-Waxer Has Removable Pads OTH the waxing and polishing pads of a new floor-waxer, which weighs only a few pounds, are removable for washing. After the wax is spread on the floor with the outside pad, it is unbuttoned and the floor polished with the dry pad underneath. New Belt-Lacing Machine Saves Time and Labor pi lacing broken belts quickly, leaving smooth and strong joints, a compact machine has been designed to save the time required by hand work. Belts not over three-eighths inch thick may be laced in a few minutes without removal from the shaft. The tool is designed not only for machine shops and factories in mending heavy belts, but for garages in repairing fan belts. With this tool a garage need keep on hand only a few rolls of belting in popular widths to make up fan belts as required. No two hook points enter the belt directly opposite each other, so that no belt fibers are broken. The machine embeds the hooks even with the belting surface. Mending a heavy machine belt Detects Artificial Pearls A SIMPLE new method of distinguish- Ing the Japanese artificial pearl from natural pearls has been discovered by Prof. Daniel Bertholet, a French scientist. He Plunges the pearl into cedar oil brilliantly illuminated with converging lights and examines it through a submersible lens. POPULAR SCIENCE MONTHLY Canoe-Sailboat Is Collapsible A NEW design of collapsible canoe that can be converted into-a sailboat, is of particular interest to hunters and fishermen. Because of its extreme light- ness it can be used on all waters with safety, it is claimed, even in shallow streams. The thrilling sport of shooting rapids loses much of its danger with this protects the cockpit from rain and splashes of water. Rigging can be added to the canoe without damage to the structure. The canoe will carry three persons comfort- ably, it is said, while allowing plenty of room in which to stow away luggage. The frame can be packed in one or two bags. canoe. Overasimple frame of pliable staves, readily as- sembled, is stretch- ed a specially de- signed cover in one piece. This is waterproof, con- sisting of canvas with an intermedi- ate layer of rubber. Another cover | a A Craft for Sportsmen Although ex- tremely light and of shallow draft, the canoe will carry a small leg-o’-mut- ton sail as shown above. Its sea- worthiness is dem- onstrated in the picture at the left, where it is seen riding easily just beyond the falls Hand Levers Drive Odd Oarless Lifeboat OWING a boat without oars is the surprising achievement made pos- sible by a British inventor, who recently designed an unusual new type of lifeboat propelled by hand levers. The purpose of the invention was the creation of a craft that could be sent away from the side of a disabled ship without the delay of adjusting oars in their locks. In place of oars, only one trained seaman to handle the tiller. The invention was demonstrated re- cently at the King George Dock, London. BECAUSE of temperature expansion and contraction, the Washington Monument is about 514 inches higher in summer than in winter. levers are provided in front of each seat in the boat. There are eight levers in all—four on each side of the craft. They are geared to a pro- peller shaft so that as the oarsmen pull them back and forth they drive a screw at the stern, sending the boat through the water. Since, contrary to the old way of rowing, no especial skill is required to operate the levers, the boat requires London, Demonstrating the new lever-propelled lifeboat at King George Dock, Geared to the propeller shaft, the levers drive the screw

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Ov. &v. Stencil Makes Bow Lips PERFECT Cupid’s-bow lips can be made in a few seconds, even by per- sons who are inexpert at make-up, it is claimed, with the aid of a newly devised beauty stencil. The flexible stencil is held firmly over the mouth so that the opening fits the outline of the lips. Rouge or a lipstick then is applied, producing the Cupid’s- bow effect. Wooden Fins for Swimmers ATHING shoes fitted with hinged wooden fins are the latest aids for the swimmer devised by a Dutch inventor. He claims that the shoes will increase the speed of a swimmer at least 10 times. When pulled forward, the fins close, and when forced out by the stroke of the feet, they open, pushing powerfully against the water. ¢ Handy Suit Box A NEW type of paste- board suit box is made in one piece, with a handle for the lid cut in the board. The box opens like a suit- case and requires no twine to hold it together. Each end of the box is rein- forced by a double piece. POPULAR SCIENCE MONTHLY Self-Soaping Brush A TWO months’ supply of shaving cream is contained in the handle of a new type of shaving brush (below) designed especially for the traveling man. Press- ing the handle forces just enough cream for a shave into the bris- tles of the brush. Floor Slabs of Concrete A SAVING of 30 per cent in building costs is said to be made possible by a new method of reinforced concrete construction. In this process small factory- made slabs of reinforced con- crete are used instead of the present method of pouring concrete in large slabs. Floors, walls, and partitions made of the small units, the inventor claims, will stand strains that reinforced concrete in one piece will not, and air spaces are provided in which wires and pipes may be laid. These further serve to make walls or partitions soundproof. A. G. Tabatchnik, a Russian architect, is the inventor of this method, which is said to eliminate the cost of wooden forms and -the laying and tying of reinforcement rods. April, ‘i935 Ingenious New Devices Fourteen Handy Products from ~- Een ans a Ro A Pocket Cigar Piercer CCASIONALLY the smoker e. counters a cigar that requires cop. siderable coaxing with a pin or other sharp instrument before it will draw satisfac. torily. It is because even the best cigars are not always perfect in this respect that the pocket cigar piercer pictured above has been invented recently. The device consists of a thimble shaped metal socket into which the end of the cigar is held. Enter. ing the socket is a small drill that is twisted with the fingers. e fe All-Sport Hand Racket FO? any of the many kinds of ball games that boys and girls play it the street or against brick walls, t light hand racket recently has been per” fected. The frame and strings are made of gut, with a thin wood backing. hand fits into an adjustable back strap. Apri fe th TE eer ow 3 — PIE IRE AOL LY CEERI R into cook the

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|, 198 er or eh 28 Con r sharp atisfac- cigars: ct that above himble- he end Enter- 1 small d with ‘ket . of ball play lis, this een per re M ng. ck strap. April, 1925 for Pleasure and Comfort the Workshops of Inventors 3 4° LE De Pia sai Reflector Serves as Stove A JOINT in the stem of this ingenious gas reflector permits it to be turned into a simple burner upon which one may cook the morning coffee. When upright the device serves as an ordinary heater. PE ae cone AION al ewe A Squeakless Porch Swing QO ELIMINATE squeaks in porch Swings, Joseph E. Morse, of Hunt- ington, Ind., has invented a hanger of ball-and-socket joints suspending the hooks to which the chains are attached. POPULAR SCIENCE MONTHLY Ferns Water Themselves F ERNS water themselves if provided with the apparatus recently devised. The soil absorbs water from a porous porcelain cone that drains water from a reservoir bottle fitted with a siphon. New Full-Length Mirror HIS port- able floor mirror in- vented by a Frenchman, _ Showsthehem of a skirt, the grace of aneck line, or the entire gown, thus serving the purpose of a full-length mirror. It is easily adjust- ed to position. Adjustable Safety Razor HE latest type of safety razor may be adjusted to any desired angle. The shaver may use it in the regular safety style with the blade at right angles to the handle, or at an- other angle, giving a diagonal stroke. Two-in-One Fans BREEZE in all directions instead of in only one, was the aim of the inventor of this two-in-one electric fan. It has two pro- pellers on the same spindle, one on each side. The quantity of air distributed is said to be increased. m | New| Suitcase porv LARITY of the Wardrobe trunk led to tH manufacture of a nevé suitease that has a coxnpartment for hats as‘ well as for shoes and soiled cloth- ing. In one half is ample space for suits or dresses, while the other half is divided into the two sections.

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68 POPULAR SCIENCE MONTHLY Home Chlorine Treatment for Colds How the new chlorine inhaler is used for the treatment of colds at home. prok treating colds at home with chlorine gas, a gas-generating inhaler recently has been devised. This is used with a special compound containing chlorine, which is given off when the sub- stance is heated. The strength of the gas is said to be easily regulated by the patient and a single treatment to cost about a cent and a half. Perfect Noiseless Plane RITISH aviation experts are reported to have virtually eliminated the deafening roar of airplanes in flight. By a new invention it is said that exhaust gases are permitted to escape noiselessly without lessening power or speed. A noiseless propeller also has been devised by an ingenious arrangement of gears. April, 1995. A special chlorine compound is used Cradle Lays Pipe Line across Straits T°? SAVE time in laying a pipe line “ from Hetch-Hetchy, the water sup- ply source for San Francisco, Calif., across the Dumbarton Straits of San Francisco Bay, engineers recently de- vised and employed the huge tilting cradle pictured above. So quickly and accurately does this mechanism place the pipe in position, that’ the engineers planned to complete the job in 60 days. The photograph shows one section of the pipe being lowered. George Taylor of the U. S. Department of Agriculture, holding the finest wire Swedish City Has Fresh Telephone Booths VERY one who has been cramped ip poorly ventilated drug-store tele phone booths, can appreciate the clever. ness of the Swedish inventor who thought of putting public telephones in boxes out of doors, on convenient street corners. The booth illustrated above is of the latest design, erected recently by muni cipal authorities in a large city in Sweden, Open lattice-work admits fresh air. World’s Finest Wire Is Too Small for Eyes to See HE finest wire ever made, wire 80 slender that it cannot be seen with the naked eye, was manufactured re cently by George Taylor, a physicist in the United States Department of Agr- culture. In the photograph at the left he is seen at work in his laboratory. Wire of this kind is not only a novelty, but a practical commodity. Among thos who use extremely fine wire are surgeons and dentists. AN EXTENSIVE business in disinfecting public telephone apparatus once a month with a new preparation called “ neroforn” recently has been developed. Machine Predicts Tire Life OW long will your new tire last? It is to the manufac- turer’s interest to know the answer to that question before the tire leaves the factory. A machine for testing the durability of automobile tires, making accurate predic- tions of the service they will give, has been devised recently by experts of the U. S. Bureau of Standards at Washington, D.C. A tire is run under standard conditions against the rim of a wheel provided with bumps. After a certain time the tire is examined for signs of failure. Weak points in the tires show up in a very short time, often in as little as two days. In actual service such a tire might last from six months to a year. Tests are made also to determine whether the chemical and physical properties of the materials are those required by the specifications and found to be necessary for the con- struction of durable tires. Measuring the durability of an auto tire with the testing machine “A steam matte usual other was la opera’ noise, The a mot of usi: used tion smoke is blov The tured Il

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h- Air S mped in re tele. e clever. thought OxeS out rners. is of the yy muni- Sweden, ir. s Too See wire 80 een with ured re ysicist in of Agri- he left he , novelty, ong those surgeons sinfecting a month erofornm” Motor-Ship Whistle Made to “Smoke’’ without Steam HE advent of the motor-ship, using Diesel oil-burning engines instead of steam, presented a real problem in the matter of adequate whistles; for the usual puff of steam that told the pilots of other ships where the whistle came from was lacking. Compressed air employed to operate the whistle produced plenty of noise, but no visible signal. The problem was solved recently when a motor-ship engineer conceived the idea of using a tank of liquid smoke, like that used in airplane sky-writing, in conjunc- tion with the compressed air. This smoke pours forth every time the whistle is blown. The ingenious new invention is pic- tured above. Illuminated Sign-Posts to Aid Tourists LUMI - NATED sign- posts to direct motorists on un- familiar roads at night as well as in the daytime were exhibited recently at a na- tional conven- tion of American road-builders in Chicago. The signs can be read in the sunlight as clearly as when _ illumi- hated at night. They will be at many important junc- tions on public hways, where ga aid y giv- ing directions. © v.& U. How the signs appear at night POPULAR SCIENCE MONTHLY 69 Unique Lifebuoy Rides Heavy Seas | ha AN ingenious new life-saving buoy, recently tested successfully in the North Sea, the victim of a shipwreck can survive in safety and in comparative comfort as long as his provisions last, the inventor claims. The buoy with its passenger rides easily over the waves, even in severe storm, it is said. A porthole in the upper part of the device can be opened and closed. It is just large enough for the occupant to thrust his arm through and fire a pistol to attract attention, as shown in the photograph. THE next eruption of the volcano Etna may be heard by radio throughout Iurope and possibly in America. Signor Marconi is establishing a new radio sta- tion on the rim of its crater and purposes to broadcast its mutterings. The occupant of the lifebuoy is able to thrust his arm through the porthole to fire a distress signal if help is near Below is a new type of mill designed to catch more ‘power from the wind Dry-Land Houseboat ‘‘Sails”’ on Artificial Lake’ b *, * dan a he lived on a hilltop, H. A. Heroux, of Oakland, Calif., longed for sea life. So he built a house in the shape of a boat, surrounded it with an artificial lake, and now enjoys cool breezes from the deck of his unique home. In the heaviest of storms the occupants have no fear of seasickness since the house is stationary, having a concrete foundation. It cost the skipper-owner, who is shown in the photograph above, $20,000 to con- struct his odd boat-house. Turns Wind Power into Electric Current N THE design of a revolutionary new type of windmill called the ‘“‘aero- dynamo,” which converts wind power direct into electric current, Major Bilau, a German inventor, believes he has dis- covered a valuable source of economical power. It is claimed that the aerodynamo can utilize 50 per cent of the wind’s energy. It differs from previous windmills in the fact that the wind wheel is placed to the lee of the tower or mast supporting it. A vane of special design, placed to the wind- ward, sweeps the wind directly to the back of the wings, where it can exert the most power. In previous types of mills the wind stream has been broken up be- hind the wheel, where the vane has been located. Thus much of the wind’s energy was lost. The photograph shows the arrange- ment of wheel and vane; also the small vanes that are attached to the wings and that add to their power.

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nit 4 18 Sanitary Kit for Baby’s Bottles and Wardrobe A BABY kit for earrying the baby’s clothing and milk when away from home has been introduced recently to take the place of makeshift bags, com- monly used for that purpose. The kit is lined with washable blue or pink rubber and in the bottom of the case are alu- minum bottle holders. Clean clothes may be packed in a pocket in the lining, while soiled clothing is carried in a rubber pocket entirely out- side the bag proper, a notable sanitary feature. This compartment is removable. The bag is waterproof and the exterior as well as interior can be washed with soap and water. Know Your Car by of the best ways to start the motoring season right is to give your car a thorough clean- ing. This should include the top and upholstery, too often neglected. Sweep off the top first. If the top is leather, a mixture made of half a cup of turpentine, half a pint of raw linseed oil and four cups of water is a good cleanser. Apply with a clean rag and rub dry. For mohair tops make a lather of a pail of tepid water and a bar of Castile soap. Use a large, clean sponge and wash the top well. Go over it with clear water to prevent streaking. Plain water with a little am- monia will remove dirt from leather upholstery, after which the cush- ions should be rubbed with a clean woolen or flannel cloth. Do not use gasoline on leather. Cloth upholstery may be cleaned by rubbing it with a sponge dipped in the following mixture: Three- quarter ounce common salt, two ounces grain or wood alcohol, mixed with clear water. Lukewarm ivory soapsuds will remove grease or oil spots. Clean all glass windows and re- flectors with a mixture of half alco- hol and half water. POPULAR SCIENCE MONTHLY Pocket Light Projects Pictures NE of the la- test novelties in entertainment is a small picture projector that can be carried in the pocket. The light necessary for pro- jection is provided by an_ electric flashlight, and pic- tures can be thrown on any white surface. When in use, a telescoping lens is extended from the case. Tiny slides are inserted in the usual way. Al- though the entire outfit is hardly larger than a pocket flash- light, the pictures are said to be repro- duced sharply and clearly. In the photograph, the picture of a lioness is projected on a smooth wall. Projecting the picture of a lioness on a white wall April, t9 ——sr AN AVERAGE of 30 per cent of the avail able power of gasoline for motors is being wasted by its discharge in the engine exhaust in the form of combustible gay according to recent government tests, entertainment. A spring balances thelone rider on this ingenious new seesaw Phone Numbers ‘Magnified by Glass Attachment MAGNIFYING-GLASS that can be attached to any telephone aids in reading small type numbers in the tele- phone book. It folds out of the way when not in use. Wet Coal Is Costly RECENT tests by the U. S. Bureau of Mines show that the wetting of coal is expensive to the consumer. Fine sizes of both bituminous and anthracite will hold up to 20 per cent in moisture, though larger sizes of the bituminous increase but little in weight when dampened. Coal can have a perfectly dry appear- ance, yet. still contain as much as 10 per cent moisture, for which the consumer pays. A moisture content of 12 per cent is not at all uncommon. Fun for. One on Spring Seesaw lee the child without a playmate an ingenious new mecha. ical seesaw operated with a spring, will provide hours of No one is needed at the other end. The spring retards the descent of the child, and helps to pull him up again after his feet touch the ground. The teeter is operated by the child’s pushing the ground with his feet, or it can be swung with a body motion. Itis equipped with a comfortable saddle and with handles to prevent the possibility of the small child’s falling off. easily from place to place. It can be moved Wires Mad Fireproof IREPROOF ip sulation for telephone switchboard wires is made _ possible by a newly discovered use for selenium, an element hith erto used chiefly in the control of electric current by light. The flameproo- ing of switchboard wires is highly important, for even a small fire can throw 4 whole exchange out of com- mission. How the magnifying glass is attached ‘Ape

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il, 19% he avail. is deing > engine le gases, tests, saw mechan- hours of id. The pull him e ground on. Iti O prevent be moved Made proof ROOF in- tion for oard wires le by a | use for nent hith- y in the ic current ameprodl- ‘d_ wires is , for even | throw 4 ut of com- _Gompact Sterilizer Aids Dentists POPULAR SCIENCE MONTHLY DEVICE that drills and attachments used in dental work continuously ster- ilized is the in- vention of Dr. P.L. Nemmers of Chi- eago, Ill. For its compactness and the ease with which it is used it was commended by dentists at a recent national dental convention. keeps other RECENT tests show that silk thread used in stringing pearls should not be dyed nor contain chemicals, other- wise the luster of The new sterilizer held by the inventor, Dr. P. L. Nemmers the pearls may be destroyed. © U. &U. Portable Electric Heater Useful as a Lamp EPCAUSE of the unusual shape of its reflector 2 compact new brass electric heater is said to focus intense heat in a given direction instead of diffusing it as does the usual bowl-shaped type of heater. For quickly heating small rooms, such as a bathroom or nursery, this fea- ture is said to be advantageous, when time is important. Its heating element is of a screw socket type that is easily renewable. An elec- tric-light bulb can be substituted for illumination, if desired, the reflector producing a powerful beam of light. The heater rests on heavy glass sup- ports. It is equipped also with an ad- justable metal bracket with screw holes, by which it may be attached to the wall in any desirable place. It is provided also with a 15-foot extension cord. It can be used on either direct or alternating current. Chicago Churches Install Offering Safes URING a crime wave in Chicago recently the collection boxes in so many churches were stolen that specially designed burglar-proof offering safes were installed in 30 churches. Three slots in the top of the safe are provided to receive as many kinds of offerings, which drop through chutes into compartments reserved for them. Sharp teeth at the end of each chute prevent the possibility of a thief’s stealing the coins by lowering a sticky substance on a string from outside. The safe is of ex- tremely heavy construction to prevent any attempt to remove it bodily. Concrete Surfacing Tool Driven by Motor INISHING the surface of concrete after the rough work is completed, removing irregularities, and preparing the surface for painting are hand processes that long have been expensive. A simple new portable surfacing machine driven by electricity recently has been perfected to do the work in much less time. Its fine cutting action is said to produce a much better surface. The machine can be used also to pro- duce special finishes on imitation stone, to cut brick walls preparatory to applying stucco, and to grind paint from bricks. In use, the motor hangs at the side of the worker, and is slung from a strap over his shoulder, leaving both hands free to operate the light power tool. How Much Science Do You Know? HEF are a dozen simple ques- tions such as might be put to you any day. How many of them can you answer intelligently? Answer each one to the best of your ability, then turn to page 144 and see how nearly you were right. Twelve more questions will appear in next month’s issue. 1. How much water is there in an inch of rain? 2. Why can deaf persons sore- times hear through their teeth? 3. What are phonograph records made of? 4. Why do bubbles collect inside of a glass of water standing in a warm room? 5. What do fishes eat? 6. Why is the moon sometimes seen in the daytime? 7. Why do moth balls get smaller and finally disappear when put away with clothes? 8. Can elevator motors interfere with radio reception? 9. Will the earth ever spinning? 10. Why does being near a dy- namo sometimes spoil your watch? 11. What is a candlepower? 12. Why do people yawn? stop

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72 An egg-beat- er that fits an ordinary drinking - glass has a combina- tion motion. A whirling — pro- peller throws the egg into the center of the glass, where it is caught by a dasher and plunged up and down until beaten enough This collapsible clothes-hanger is useful for hanging dresses, coats, or trousers. The sliding sides are ad- justable to several sizes and allow easy packing. The top hook folds in ia £3 f fi POPULAR SCIENCE MONTHLY science Eases the Labor New Fixtures for Kitchen and Bedroom The flexible metal nozzle of the oilcan at the left makes it invaluable for reaching awk- ward corners in the carpet- sweeper’s or the vacuum cleaner’s out-of-the-way joints Keeping a comb clean is an easy matter with the device shown above. It is held like a razor strop, hooked at one end to an adequate support Double shoe-trees keep shoes to- gether on a hanger. Pressure is ex- etted from arch to toe, leaving no strain on the heel. A small hook in the center hangs the trees on the rack t ee | % A hair-drying comb will prevent colds after shampooing. One part of the comb is heated, then inserted into the comb proper, which being of aluminum, readily conducts the heat An automatic stand for the electric iron _pre- vents overheating of the iron, as the current runs only while the iron is in use or off the stand 195 Slicing eggs or beets can be accom. plished neatly and quickly by this device, which is made of a grid of fine wire that is pressed through the food A rubber base with small projec. tions keeps this new sugar dispenser from sliding over tables that have polished wood or glass tops. The ~~» base is removable for washing oJ we] Clothes-hangers to suit every need can be found nowadays. The one above is particularly useful because it will swing three ways and collapse or ex- pand as the occasion demands

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L, 199 oT om

accom. 2< BE eo zg projec- spenser at have washing

April, 1925 POPULAR SCIENCE MONTHLY 73 of the Modern Housewife Simplify Many a Home-Making Problem

To prevent drafts, a light, strong strip of bent metal is designed to be slipped under the door and fastened by two screws. Tightening the screws adjusts the strip to its frame

A cone-shaped aluminum egg- separator that fits on top of an ordinary tumbler, prevents broken yolks. The white runs slowly through a slotted section, leaving the yolk in the top of the metal separator

This new dish-dryer has gradu- ated bins that keep delicate and heavy china separated, prevent- ing much unsightly chipping

Fish-scaling will be found a less disagreeable task with this new scaler. The handle is ele- vated so that the hand grasps it easily, and the many teeth finish the unpleasant job quickly

the beam automatically lowest visible number indicates the weight of one dozen eggs of This safety can opener keeps the can at a distance. Turning the key clockwise makes the can revolve, and a sharp-edged steel wheel neatly cuts off the top A stool in the kitchen means rest for the housewife. This white enameled seat that swings in under the sink will save nerves and backache and insure cheerfulness and added efficiency Even children can grade eggs with this new invention. When an egg is put in the grader,

SAE RR ee ee Ore er tt. Le fae

Mayonnaise can now be made under a fau- cet. When the water is turned on, the beater revolves, while oil drips slowly from a _ con- tainer above the bowl

resents ie tS Cp ¢ | =e

This built-in garbage receiver is convenient and sanitary. When the docr is opened, the can swings out with it. The hinged metal door keeps in unpleasant garbage odors adjusts itself. The the same _ content For condensed - milk or syrup containers this can- opener and spout is useful. A sharp point is pressed into the lid and given half a turn to fit it snugly into the hole

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How to Build POPULAR SCIENCE MONTHLY a April, 1925 Radio-Frequency Amplifier — 3 3 6 Fig. 1—Rear view of two-stage radio-frequency amplifier, showing layout of parts and wiring. oS. 4 3S The parts are lettered and numbered to correspond with wiring diagram below. met Note brass brackets supporting the tuning units. These were made by bending the ends of right-angle brackets tive receiver, the chances are that you are wondering how you can add radio-frequency amplification without having to rebuild your whole outfit. This article will show you how to do it. And there is nothing tricky about the circuit either—anybody who can get a regenerative receiver working properly will have no trouble at all in adding two stages of radio-frequency amplification to his set. Do not build this radio-frequency am- plifier with the idea that it will increase the strength of the signals from powerful local stations, for if you already use a good outdoor antenna, there will be no appreciable increase in the volume; that is not its mission. Radio-frequency amplification will be a big help, however, in bringing in distant stations, and—-what is still more impor- tant to many radio fans—it will greatly increase the selectivity so that you will be able to get the distant stations right through the locals when conditions are at all favorable. If you follow the instruc- tions carefully, you should have a set that will give the greatest satisfaction. I’ YOU already have built a regenera- [PIGURE 1 shows a wiring dia- gram of the radio-frequency amplifier, and you will note at the right a coil marked X. This is the coil used to couple the radio-frequency amplifier to the receiver you now have. De- tailed instructions on how to use this coil will be given further on. Hooked to an ordinary re- generative set, this amplifier unit enabled the writer—in New York City—to bring in WTAS at Elgin, Ill., and several other distant stations with plenty of volume early in the evening when ail the locals were on the The Parts You Need: A and B—First tuning unit C and D—Second tuning unit E and F—Variable condensers, .0005 mfd. maximum capacity G and H—Rheostats I—400-ohm potentiometer J and K—Vacuum-tube sockets L—Panel, 7 by 18 inches M—Wooden baseboard, 6 by 17 inches N—Binding-post strip, 34 by 6 inches Two pieces of composition tubing, 3 inches in diameter by 3 inches long; two dials (if they are not included with the variable condensers); six binding posts, brass right-angle brackets, bus wire, and wood screws. air. The same stations could not be tuned in on the regenerative receiver alone without considerable interference from the local stations. . The radio-frequency-amplifier unit adds two tuning controls, to be sure, but since it eliminates the need for a tickler in the regenerative set and also dispenses ti tk Fig. 2—Wiring diagram. ae —; [ 90 VOLTS The coil X is built into your receiver, as shown in subsequent diagrams (Figs. 7, 8, and 9) HIS simply de- signed unit of one or two stages can be added to your present set without rebuilding. ft will bring in the distant stations more clearly, By Alfred P. Lane with antenna tuning where this is used, the total number of tuning controls re mains at three—the two dials of the radio unit and the dial of the secondary con- denser or grid variometer in your present set. It is quite possible that the radio frequency amplifier as illustrated does not match the design of your present receiver either in size or in the arrange- ment of the binding posts. HE panel L was made 7 by 18 inches because so many radio constructors favor this size and the binding posts are mounted at the back on strip N, since this is the style at present. If your receiver is built with the binding posts on the panel, you can follow the same style in the _ radio-frequency-amplifier unit by placing binding posts Nos. 1 and2 at the left end of the panel, as seen from the front, with binding post No. 6 at the right end opposite the antenna binding post of your present set. Leave the re-. maining four binding posts, which are for the battery connections, where they are shown in Fig. 1. The radio-frequency-amplifier unit will give best results with 14-ampere storage-battery tubes and 90 volts of B battery; but dry-battery tubes can be. used with satisfactory results, although it may be necessary to add three or four turns to coils C and X when the smaller tubes are used. You will note that there is no binding post for the minus- a B-battery connection. This has been left out purposely. Ordi- narily the minus-B-battery bind- ing post is connected with the plus-A-battery binding post, but since this connection with the o+p _ filament circuit has been made pin. already in your present set, it Is cceNNG useless to do it again. Besides, if by chance the minus-B-battery lead in’ your set is connected with the minus-A-battery wire instead of with the plus, an addi- tional connection in the radio- | TA wAC Nn vi ~A A \ * + aor a,Yr sui ten 40( hig the bat lay in | the

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; Te- adio con- sent dio- does sent nge- ches tors are: ince your osts ame ‘ifier nd 2 ‘rom , the ding > Te, 2 for are unit pere of B ough four 1 the is no inus- Yrdi- yind- . the , but - the nade it is es, if ttery acted addi- adio- april, 1925 -amplifier unit might eT anit your storage A bat- tery with rather disastrous results to the wiring, to say nothing of the effect on the battery itself. HE tickler coil, or plate T variometer, should be cut out of the plate circuit of the detector tube in your set when used with this radio-frequency-amplifier unit because you can get the set up to the point of oscillation on any wave length by adjusting the po- Fig. 3—Panel layout. eter J is shown between the two condenser dials. : oscillation. Place the binding posts on panel if you so desire POPULAR SCIENCE MONTHLY The knob controlling the potentiom- It controls 78 means of brass brackets, as shown in Figs. 4, 5, and 6. Coil A con- sists of 8 turns of No. 22 double silk-covered wire centered on the tube. The terminals of this coi) are brought out as shown in Fig. 1, where they are convenient to binding posts 1 and 2. Coil B consists of 25 turns on each side of coil A, with the inside ends of the two sections soldered together inside the tubing. The direction of winding makes ne difference in any of the coils ex- tentiometer I. bs : 15 > f. copt own the ge fame of ae There are many other ways to an must be wound so tha control oscillations in radio-fre- > +9" t the current flows in the same ifvi circuits be- direction around the coil from Soe the ier: and some f ‘les oe ee ee i - one end to the other. f them could be used very well ey, iol i ; in place of this instrument in the ¥ = z : "| ; | De prctnn sy. way to fasten em ifier as constructed. How- | rot fe lt i She ends of the wire is to dri _ the potentiometer arrange- Y [és ——- —o—. — +. sn rk \ two small holes about one-quarter ment is foolproof, and a slight ad- a a ae a a ee of an inch apart where the-end of justment of it will compensate for ’ 4 os * a the wire is to come, and pass the variations in different tubes, coup- ling between stages, and so forth. The use of a separate rheostat for each tube is worth while, since often two tubes have slightly different characteristics. One tube may require a bit more current than the other for best results. Those fans who desire to build a one- stage radio-frequency-amplifier unit in- stead of a two-stage can do so very easily. Just eliminate parts C and D, F, H, and K, and connect the plate terminal of socket J with binding post No. 6 instead of with coil C. T= parts you will need are listed on page 74, The sockets J and K and the rheostats G and H should, of course, be chosen to suit the tubes you use. A 200-ohm po- tentiometer will do just as well as the 400-ohm one specified, although the higher the resistance of the potentiometer, the less current it will drain from the A battery. After you have bought all the parts, lay out the panel according to the diagram in Fig. 4. Note that only the location of the holes for the shafts of the instruments Fig. 5—Right-end view | Fig. 4—Diagram for drilling the panel, with exact measurements indicated. Only the holes for shafts are given. Lay out holes for A should be one-quarter inch supporting screws from templets supplied with the instruments is given, since so many instruments are single-hole mounting, and the ones that require holes for mounting usually are supplied with templets. The easiest way to drill the panel without scratching it is to mark off the locations of the holes on a piece of paper the exact size of the panel. Then paste the paper on the panel with library paste and drill the holes right through the paper after you have made a deep center punch mark for the center of each hole. After the holes are drilled the protecting paper can be washed off. AUDIO AMPLIFIER { 1 TO +B AMP. 4 BINDING POST Fig. 7—This wiring diagram shows how to connect the radio-frequency-amplifier unit with a single-circuit set. Coil X should con- sist of four turns of bell wire wound around the secondary coil. All parts and wires shown in dotted lines should be eliminated The panel is fastened to the baseboard by means of four round-headed wood screws. The locations of these screw holes are included in the panel layout in Fig. 4. Mount the instruments on the panel as shown in Figs. 1, 5, and 6. It is well to set the condensers E and F with the plates up instead of down to allow more room for the coils. The winding of the coils is the next step. They are wound on composition tubing 3 inches long by 3 inches in diam- eter and mounted on the baseboard by wire through and back. The two pairs of holes for the ends 6f coil apart and the two holes for ends of coil B, which are nearest to coil A, are naturally the same distance apart. Only two holes are necessary for the two ends, since they are soldered together inside the tube as shown in Fig. 1. Each half of the winding of coil B is three- quarters of an inch long and you can drill the four holes for the outside ends of coil B on the opposite side of the tube 134 inches apart. Tuning unit CD is just like AB, except that all the wire ends are brought out on the same side. Coil C consists of 4 turns of No. 22 double silk-covered wire and coil D is wound with 25 turns on each side of coil C. After you have mounted the tuning units AB and CD, the sockets J and K and the binding-post strip N with six binding posts screwed to it, all on the base- board M, as shown in Figs. 1, 5, and 6, you are ready to proceed with the wiring. The coils AB and CD should be set on the baseboard so that the axes of the coils make an angle of about from 55 to 60 (Continued on page 149) Fig. 6—Left-end view

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riage

2 rete seape r 4 Alternating POPULAR SCIENCE MONTHLY

April, 1925 Light Current Will Do the Work of B Batteries This Filter Circuit Should Cost Less than $10 to Build N PREVIOUS articles in | POPULAR SCIENCE MONTHLY, I have shown how to use farm lighting current and ordinary direct current from the street mains for supplying the B-battery voltage. needed by radio receiving sets. In this article I shall describe how you can use alternating current for the same purpose. This method is relatively more important be- cause the majority of radio fans throughout the country are located where only alternating current is available. The first step in ar-- ranging to use this cur-

By Alexander E. Senauke, M.E. peg NO SET = /? =

A house-furnishing store will sell you the mason jars, the grocery store keeps borax jn stock, and the plumber can supply the sheet lead and the fiber wash- ers, shown in Fig, 3 which are used as insu- lators. The pure sheet aluminum is not so easy to obtain, but your hard- ware dealer will put you in touch with a source of supply if he has none in stock. The total. cost of the four cells ready for

rent for your radio set SO-I00-WATT 7) “ia use should be less than is to rectify it. Figure 1 LAMP ——> | } STORAGE BATTERY i} one dollar. gives a good idea of the a cue result of this operation. neue ofp ALUMINUM bene porcelain lining At the top is a curve POLE SW . Cates L in the caps of the representing alternating | C, 3 broken out with a light house, and just below it NO VOLTS >! ee 1 hammer and then. the is another curve showing nlite siecieties L holes drilled as indicated, the current as it leaves Make the holes at least ALTERNATING CURRENT SUPPLY the rectifier. You will note that none of the diagrams show how to use alter- nating current as a sub- stitute for the A battery my) oy ALTERNATING CURRENT D\PDDADAAS AFTER RECTIFICATION What the Rectifier Does Fig. 1—The top curve represents the alter- nating light current that is supplied to your house, while the lower curve illustrates how it leaves the rectifier as direct current

as well as for the B battery. It is pos- sible, of course, to build a current-rectify- ing device that will eliminate all batteries, but the construction of such a circuit is beyond the scope of

ALUMINUM 77"

The Hook-Up to Your Set Fig. 2—This diagram shows how to wire the parts of the rectifier and connect it with your set. The values of the inductance, re- sistances and condensers you will need are given in the table at the foot of the page Standard one-pint jars are very satis- factory. The way to fasten the lead and aluminum plates to the cap of the jar is shown in Fig. 3. The aluminum plates should be made of the purest material ob- tainable and the area of aluminum below the top level of the solution in the jars should not be more than one square inch. The size of the lead plates is not important —two or three square inches of sheet lead will do for each cell. The solution in the jars should consist of distilled water in which has been dis- solved as much ordinary borax as the water will take. one quarter inch in diam- eter so that you will have no difficulty in centering the screws that hold the alumi- num and lead plates to the tops. After you have the cells assembled, TWO 6-32 BRASS SCREW FIBER WASHERS

How to Build the Cells Fig. 3—Standard pint mason jars are used in constructing each of the four cells constituting the rectifier unit. This diagram shows the method of attaching the plates to jar top test them to make sure that none of the screws touch the metal of the cap. This can best be done by putting the cap and the screws, one at a time, in series with a dry cell and an ordinary buzzer or bell. If the bell does not

ordinary amateur work. Figure 2 shows how to lay out and hook up a complete B-battery climinator that will work on 110-volt alter- nating current of 50 or 60 cycles such as or- Number of Inductance Allowable D.C. C C C dinarily is supplied for Tubes of L Resistance of L ~*? = = house lighting. 3 5-20 henries 2000 ohms 2 mfd. 4mfd. 2 mfd. The four mason jar rectifying cells at the 5 1500 ‘ ek a 2 bottom of the diagram 7, 8,or9 1000 “ gs : ke constitute the rectifier portion of the unit.

inductance L, the condensers C,, according to the number of tubes in your set: The Values to Use with Your Set The following table tells you the values you will require for the C2, and C;, and the resistance R, ring, there is no short circuit. Be sure to drill a small hole about one sixteenth inch in diam- eter in the center of each cap to serve as a vent for the gases that form while the rectifier is in operation. It is not absolutely necessary, of course, to build the rectifier cells in mason jars. They (Continued on page 151) R 5000 to 10,000 ohms, variable “a ‘ sé 4

April

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April, 1925 . POPULAR SCIENCE MONTHLY The Month’s Novel Radio Ideas New Inventions for Receiving Sets and Broadcast Stations Tiny Station Although thousands of amateur radiophone stations use power as low as five watts, WDBX in New York City is the only regu- larly licensed radio broadcasting station in America with only one five-watt tube to supply energy to the antenna. Samuel Mc- Mullen is shown at the relatively tiny control board of WDBX Grandfather’s Clock Up to Date This modern version of the grandfather’s clock attracted considerable interest at the first radio show ever held in Germany. It is wound auto- matically and is set for the German standard time by radio. A loudspeaker for broadcast reception is just below the pendulum, while a receiving set and battery compartment take up the rest of the space in the cabinet. In this view the tall door cf the cabinet is open to give access to the neatly arranged radio set Giant Tubes for Oversea Radio Here is one of the new water - cooled vacuum tubes that are being man- ufactured for the British Government wireless sta- tion at Rugby, England, to be used for radio com- munication with New York. They are said to be many times more powerful than any tubes now in use. The valves are tested with a current at a voltage of 15,000. The operator stands by with a cord connected with the power supply 80 that it can be shut off from the tubes instantly M case of an emergency New Coils Give Sharp Tuning When a receiver employing several stages of radio-frequency amplification is used near a powerful broadcasting station, the coils themselves act as loop antennas so that it sometimes is difficult to tune out the local station. Qne manufacturer claims to have solved this trouble by shaping the coils like a binocular and eliminating interstage coupling. Radio waves reaching the coils, except by the antenna, are balanced out Saves Tubes Owners of radio receiving sets installed in homes where there are small children will appreciate the advantages of locking up the receiver when it is not in use. This switch leck takes the place of the ordinary switch operated by a button. The key turns off the filament circuit so that the set cannot be used

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greta AOA ciate ts ae SS a eS a pet How to Sel \ FAR as quality of reproduction is concerned, the radio receiver and the loudspeaker are the Siamese Twins of radio. The former converts the high-frequency radio im- pulses into much more powerful electrical pulsations at audible frequencies. These, in turn, are transformed into sound vibra- tions by the loudspeaker. Should the radio receiver deliver distorted electrical impulses to the loudspeaker, the result is bound to be poor reproduction. And it is equally obvious that nothing but unsatisfactory speech and music can come from a low grade loudspeaker, no matter how perfectly the radio re- ceiver itself performs its functions. People who possess an ear for music naturally are in a better position to pass on the musical quality of a loud- speaker. It is unfortunate that some radio dealers ap- parently have no ear for music at all, judging from the raucous blare they persist in sending out over the public streets by way of loud- speakers installed in transoms over doors. In almost every case of this kind, quality has been sacrificed in order to attain the maximum volume, and the ears of passing pedestrians are assaulted by a noise well calculated to drive any thought of owning a radio receiver out of their heads. This brings out one point that POPULAR SCIENCE MONTHLY April, 1925 ect Your Loudspeaker An expert helps you choose an instrument that will give undistorted reproduction of radio voices and music By Arthur A. Stuart clearly if you are in the same room with the loudspeaker? This is a vital point, for upon it hinges the amount of money you will have to You can judge whether a loudspeaker pro- duces good quality by listening with head phones on the detector stage, then listening to the loudspeaker, and comparing the two attempt to get the music or gs enough to be heard all over the means _ tortion has to be compensated for in eve possible way—and this means carefy] de. sign, precise manufacturing methods, and much testing and adjusting. Natural}: the cost of such loudspeakers is high, . It is claimed by experts that a £00d pair of head phones costing less than $10 will give you as good, if not better reproduction than can be ob. tained from the very finest loudspeaker money can buy. This is because the head phone is called on to give out sound vibrations of relatively small magnitude. To understand what causes the distortion, it is necessary to know something of the mechanism used to transform the electrical impulses into sound vibrations in the air, The head phone is the sim. plest example. It consists of a permanent magnet arranged so that the poles of the mag- net exert a constant pull ona thin disk of iron called the diaphragm. Coils of fine wire are placed on the poles of the magnet in such a way that the magnetic effect of the electrical im- pulses from the radio receiver change the pull of the permanent magnet on the diaphragm and it moves back and forth in time with the electrical impulses. The vibration of the diaphragm is what causes the sound waves in the air. The permanent magnet natur- is important—you cannot always rely on the dealer’s opinion as to the best loudspeaker. It is a question you must decide for yourself, and if you have no ear for music you should call in some friend who has the ability to help you. The advice of any reliable radio dealer can be depended on with respect to all other items of your radio equipment if you will tell him exactly what you want in the way of results, for the factory- ally exerts the strongest pull on the diaphragm if placed very close to it, and this fact accounts for some of the distortion. Strong electrical impulses cause the iron diaphragm to vibrate so far that it bumps against the ends of the pole pieces with a _ chattering sound, and if the spacing is in- creased, the weaker impulses are lost altogether. Many loudspeakers are equipped with an adjustment to regulate this spacing to compel- made receivers of today are nearly all capable of excellent re- sults as far as quality is concerned. Perhaps the first question to be decided is the matter of volume. Do you want to fill the house with music or will you be satisfied with enough volume so that you and your friends can hear A typical homemade loudspeaker, consisting of an old phono- graph horn to whichis attached a single head phone. Such an outfit will give excellent quality of tone at low volume spend for a loudspeaker. Volume and quality do not go hand in hand. High quality with small volume is relatively easy to attain, but the minute you Beware of the loudspeakers that over-emphasize a few notes on the musical scale or a few tones in the human voice sate for loud signals, strong plate current, and so forth. In a num ber of models, the diaphragm is made of mica or aluminum con nected with a small piece of iron, called the ‘armature,’ placed in the field of the permanent magnet. The connection (Continued on page 248) April S and 1 a ser ceive idea were signa He that | in des maga He ez amat along befor const main versa circle’ Ma radio saw possi catch pieces ratus on th lengtl pear tagge words Ra terest soon | maker ratus, qualit could the r: out a boxes. in spit parts loss”’ label 1

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loud >, dis- every ul de 3, and urally . d pair 1 $10 etter, De Ob- finest 1 buy. head ve out tively Causes essary f the sform Ss into 1e air, e sim- sts of a ranged e mag- ll on a ed the 1e wire of the y that cal im- uge the on the ‘orth in . ee ; CAUSES natur- pull on 1 very ecounts Strong he iron ar that 3 of the attering y is in- lses are are nent to -ompen- ag plate a num- ragm is 1m con- 1, called field of inection April, 1925 What Does “Low Loss” Mean? POPULAR SCIENCE MONTHLY 79 A much-abused radio term explained to safeguard you against inferior parts parading under false colors of radio, a young man who was inter- ested in amateur radio transmission and reception on the shorter waves, made 4 serious attempt to design a radio re- ceiver for use on these waves with the idea of reducing some of the losses that were hampering his reception of distant signals. : He succeeded in working out a receiver that gave uncommonly good results, and in describing his outfit for one of the radio magazines, he hit upon a brilliant thought. He called it a “‘low-loss” receiver. Other amateurs experimented along similar lines, and before long ‘‘low-loss”’ construction was the main subject of con- yersation in amateur Gor time ago, back in the dark ages circles. Manufacturers } of radio apparatus quickly saw the advertising possibilities of such a catch phrase, and new pieces of radio appa- ratus designed for use on the broadcast wave lengths began to ap- pear on the market tagged with the mystic words, “‘low loss.” By John Carr smooth surfaces on both sides, or they may be punched out in a press, with the result that they are burred on one side and bent on the other. After assembly, the punched washers are polished on the out- side and they look well to the prospective buyer, whether they are making good contact with the plates or not. The qualities that entitle a variable condenser to be called ‘‘low loss’? may be stated in a few words: Good insulation in the right place and not too much of it, Radio fans were in- terested at once, and soon it looked as if no maker of radio appa- ratus, regardless of the quality of his product, could possibly stay in the radio game unless he, too, brought out a line with the magic slogan on the boxes. And that condition exists today in spite of the fact that a number of the parts now on the market labeled ‘‘low loss” have no more rightful claim to the label tran the man in the moon. , possible. ‘THERE is no mystery about the “low- loss” idea. A ‘‘low-loss’’ condenser is simply one that performs its electrical functions in a highly efficient manner. Because a variable condenser has metal end plates and a grounded rotor does not prove that it is electrically efficient. Asa matter of fact, it may actually have greater losses than a condenser with molded end plates. Care in construction and the quality of the materials used are more important than any particular style. Every new model brought out by a reputable manufacturer is quickly fol- lowed by a number of imitations. Out- wardly, at least, two condensers may appear to be equally good, but one con- denser may be insulated with the best material obtainable, while the imitation contains insulation like the original only in color and finish. Spacing washers may be turned out by screw machines with perfectly flat, Notice that the tuning coils are How Not to Build Your Receiving Set The receiver pictured above is a_ typical example of what not todoif you want your set to be of “‘low loss’? design—one that will bring in signals as clearly and as loudly as accurately spaced plates making good contact with the shaft and fixed support, and rigid bearings. The matter of bearings, by the way, is important both electrically and mechan- ically. We must rely on them to main- tain the moving plates in permanent alignment with the stationary plates, and no condenser can be rated as first class unless the bearings have absolutely no side nor end play. Otherwise it will be impossible to be sure of always hearing the same station at the same point on the dial. Good bearings also are of great impor- tance in the actual operation of a receiver. A bearing that turns with a smooth, vel- vety motion makes close tuning possible without Vernier dials. ‘Ts condensers made by reputable manufacturers vary somewhat as to electrical efficiency, but the differences are so small that even the poorest one of the lot still would bring in any signal that could be heard by the best one. Nearly all tuning coils and inductances of various kinds now are labelled “low loss.”” And many of them are really ex- ceptionally efficient. They are wound with the finest grade of wire, use the placed at one end of the panel and the tuning condenser at the other, with two-stage am- plifier between them. While this arrange- ment looks well from the front, the long leads in the secondary circuit produce distortion minimum amount of supporting insula- tion, and actually live up to the claims of the makers. Others are “low loss” in name only. They are wound with a poor grade of wire, often with defective insula- tion, and with metal braces in the wreng place. The various forms of basket- weave coils have attained a considerable degree of popularity lately, but you can bank on it that the preduct of any of the reliable manufacturers will bring in the signals provided the other parts in the receiver are right. ANP this is a very important point. You can take a really “low-loss” condenser, a correctly designed tuning unit, and suffi- ciently high grade parts to build a receiver, and yet if you place the parts in the set in the wrong position with re- lation to each other, you will lose all. the value of the “‘low-loss” construction in the in- dividual units. In the first place, do not build a receiver in which the tuning coils are so placed that any large mass of metal is near the open ends of the coil. If you place a good “‘low-loss’”’ coil against the condenser plates, for instance, it will have far higher losses than the worst coil properly placed. An audio- frequency transformer produces an effect that is even worse than condenser plates when placed in the field of the coil. If you want to know what metal does when placed in the field of a tuning coil, just hold a tobacco tin flat against the end of the coil when the set is in operation and see what happens to the signals! FTER all, a “low-loss” receiving set is one that brings in the signals as clearly and loudly as possible. To gain the advantages that are inherent in “‘low- loss” parts, the amateur builder should be willing to sacrifice appearance to have the instruments placed most efficiently. Perhaps one of the worst examples of poor design is the practice of arranging the tuning coils at one end of the panel and the tuning condenser at the other, with a two-stage amplifier located in between. Such an arrangement looks well from the front, but what can be said of the long leads in the secondary circuit? Distortion is almost sure to occur because of the capacity effect between the long connection with the grid of the detector tube and the audio-frequency wires, which often parallel it for many inches.

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eee RB ELL COED EAT AIRE POELLES t rns oay tier Gere tox: It takes the average driver half a second to jam on the. brakes after an emergency has presented itself, Dur- ing this mental delay © the car travels many feet. How quickly do you act in a crisis? mobile at 30 miles an hour. Ap- parently the road is clear, when sud- denly a siren shrieks and a_fire-truck thunders from a side street directly into your path. How quickly can you stop? If your car is equipped with four- wheel brakes in perfect condition, you probably can bring your machine to a standstill within about 38 feet. And you will be borne out in this, apparently, by recognized charts of braking performance. But actually, can you? You may know that your car’s braking mechanism will respond instantly to your foot on the pedal. But what about the speed of your mental machinery? How quickly, after your mind senses an emergency, can you jam on the brakes? The answer to this question, as the result of recent discoveries by the U. S. Bureau of Standards, suddenly is re- vealed as a factor of tremendous impor- tance in the appalling toll of death and injury from traffic accidents. For these discoveries, made with ingenious new measuring instruments, have demon- strated the surprising fact that for the average driver an interval of at least half a second elapses from the time he senses a warning of danger until he can jam on the brakes. And in this half-second interval of delay a car speeding at 30 miles an hour will travel a distance of 22 feet before the brakes are applied! GS motte you are driving an auto- | bo OTHER words, instead of being able to stop your car with four-wheel brakes within a distance of 38 feet, as you believe, the distance actually will be nearly 60 feet, if you are an average driver. And if you are below the average in quickness of mental response, the dis- tance will be even greater. These amazing new measurements of the mental slack in relation to safety on the road are more than substantiated in American traffic courts, where, every day, comes tragic evidence of the mental By Robert E. Martin POPULAR SCIENCE MONTHLY How Quickly OU are driving along at, say, 30 miles an hour. A shriek from a siren! A fire-truck darts out from a side street! ; How fast do you apply your brakes? “Instantly,’’ you answer. You are wrong. The Bureau of Standards, investigating the ‘‘mental slack’’ of motorists, finds there is an interval of almost half a second between the time an emergency calls for brake action and the time most of us actually apply the brakes. In this half-second your car can travel 22 feet! April, 1925 Your Bureau of Standards to Test Your paralysis with which motorists are afflicted in the face of emergencies. There col- lisions and wrecked lamp-posts pass jp constant review before the judge on the bench. There the drivers of automobile appear at their worst—drivers whog mental alertness has been put to the test and has been found wanting. A BALTIMORE judge recently told me of a man who was driving his car with tne stream in a crowded street. A movement of cross traffic had just ceased, and the motorist moved ahead with his mind settled upon the idea that for several blocks he would enjoy uninter. rupted progress before he would be stopped by the next intersecting stream of traffic. Normally this state of mind would have led him into no difficulties, But in this particular case, he encountered the unexpected in the form of fire appa- ratus speeding directly across his path. There was no failure of signals and no lack of warning—a fact that was shown by the circumstance that all the cars behind this man came to an immediate stop. He was the one driver who failed. Not until he was within striking distance of a fire-engine did he attempt to apply his brakes. By this time, of course, his efforts were useless, and a bad smash resulted. Slow thinking cost the man severe injuries, a seven-passenger car, and traffic-court discipline. And there was nothing wrong with his brakes. This is what sometimes happens as a sequel to delayed mental response—injured passengers and a wrecked car because a driver’s brain was half a second late in responding to an emergency! April, 19 C Dev: Men Just bh was clea between spot at W car imms interval proving t his brake not rema tion, in c dear chai peremptc the fire a Incider without valuable the slack is sufficie: might he the auto: more tha 18,000 in The r shown th:

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y l rds ur Hicted € col. ass in on the L0biles whose he test ly told his car et. A ceased, ith his ‘at for ninter- uld be stream f mind culties. intered - appa- path. and no shown ne cars nediate » failed. listance 0 apply rse, his smash 1e man par, and . are Was quel to ers and in was rgency! April, 1925 Can You Car? Devises New Ways Mental Speed Just how slowly his mind responded was clearly established by the distance petween the point of collision and the spot at which full stop was reached by the car immediately behind his own. This interval of clear space measured 36 feet, proving that he had ample time to apply his brakes and halt his car if his mind had not remained frozen. His sole explana- tion, in court, was that he had expected a dear channel and had not “taken in” the peremptory warning of the approach of the fire apparatus. Incidents such as this might be cited without number. Again and again a valuable fraction of a second lost while theslack mind is registering an impression issufficient to carry a car to disaster that might have been averted. Meanwhile the automobile death list grows, from more than 16,000 in 1923 to more than 18,000 in 1924. The research of psychologists has shown that mental slack is as definite as POPULAR SCIENCE MONTHLY Stop the sag in a towrope or in the couplings of a freight train. In each case there is lost motion. -The captain of a tugboat knows, from experience, how far he must travel before the sag of his line is taken up. Likewise, the locomotive engineer, from his cab, can judge with equal accuracy when his train is pulling smoothly. Now science has applied actual measurement to the BRAKE APPLIED i } Pee ee eras ous ae WARNING SHOT An official of the U. S. Bureau of Standards making a brake test with the decelerometer, a new instrument that measures the time required to stop acar. At the left is a close-up of the instrument, without its case The pistol test of mental delay. Bullets of red lead mark the toadway, providing a means of measuring the distance traveled between the warning shot and application of the brakes A car with four-wheel brakes, travei- ing 30 miles an hour, can be stopped within 38 feet after the brakes are applied. But recent discoveries show that in the average half-second interval of mental slack between a warning signal and application of the brakes, the car will travel 22 feet time required to take up the slack in human thought processes. In the Bureau of Standards tests, government scientists are making available to every motor-car driver valuable new measurements that will give him more intelligent control over his car and assure his greater safety. The apparatus used in the tests em- ploys two pistol shots fired from a moving automobile. The first pistol is fired by a judge or inspector riding behind the driver. It represents a danger signal—a peremptory command to apply the brakes. In response, the driver jams on the brakes as quickly as he can, and the pressure of his foot on the brake pedal automatically fires the second pistol. Each bullet, fired downward from the car, is made of litharge, or red lead, which produces a red mark on the roadway. The two splotches of litharge tell the story of the driver’s mental alertness or. . laxity, for the distance between them . represents the travel of the car during the time he spent thinking about applying the brakes and in moving his foot to the pedal. In addition, the time required to bring the car to a stop and the rate of slowing down are measured by a recording decelerometer, an ingenious instrument designed especially for the purpose by engineers of the bureau. In the Washington testis the quickest time for any driver was a quarter of a second, the slowest was six-tenths of a second, and the average was close to half a second. The best showing was hardly to be counted, for the reason that the driver had his foot on the brake pedal at the firing of the first shot. In all the other (Continued on page 147)

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82 POPULAR SCIENCE MONTHLY April, 1995 Shortcuts for Car-Owners Simple Light Holder \ ,' JHEN working on your car at night, you often wish you had an extra hand to With the little device shown in Fig. 1 the lamp may be clamped on your head so that the beam of light is kept automatically on the spot where you are hold your pocket flashlight. working. The flashlight is held in a clip made from strong wire fastened with four rivets to a small piece of sole leather. This in turn is riveted to a skate strap. When some inaccessible spot is to be reached with a screwdriver, the lamp may be strapped on the wrist.—F. S. Root, Fall River, Mass. LTHOUGH spindle-body bushings frequently need replacement, the removal of the old bushings often pre- vents the job from being done in the home garage. One car-owner, however, makes use of the method illustrated in Fig. 2. A saw cut about 11% in. deep is made in an old spindle bolt, which then is inserted in one end of the spindle body and pushed to the lower end of the opposite bushing. The head of the bolt is placed on an anvil, and a small chisel or wedge is driven into the saw cut so that the spread end will engage the end of the bushing. A few hammer blows on the bolt head removes the bushing. The opposite bushing is removed in the same way and new bushings are driven into place == an INK \ PR Wy \ and filed off to eee |) fit the yoke.— i Fig. 2—Removing spindle bushings HAROLD N. WHITMORE. ECHANICS who park their cars out- side a factory or building under construction from morning till night often find that a blanket thrown over the engine hood has been blown partly or entirely off and the en- gine has been chilled nearly to the freez- ing point. As appearances usually do not matter, it is a simple thing to use an old tire, as shown in Fig. 3; to hold the blanket over-the engine. At night the tire section can be thrown into a corner of the yard for use on the next cold morning.—L. B. RosBBINs, Harwich, Mass. WOODEN TOP AND BOTTOM Fig. 5—Folding pitcher ON ONE occasion when my regular tube repair kit was not large enough to repair a long blowout, I laid the tube on a piece of strap iron, placed my cement and repair rubber in position, covered it with wax paper, put a piece of tin over the Fig. 1—Strap and wire clip hold flashlight in best position for illuminating the work Ril: Fig. 3—Old tire prevents radiator blanket from being blown off in a high wind SEB MOVING stating —— Fig. 6—Tool for extracting ball-bearing races hole and tightened down my clamps. Then I saturated a length of sash cord in gasoline, laid it on top and lit it (Fig. 4). This made a serviceable repair.— OscaR M. ANDERSON, Tacoma, Wash. A COLLAPSIBLE pitcher for filling automobile radiators can be made as shown in Fig. 5 from a section of old inner tube fastened with shellac.and tacks to a wooden top and bottom. Both should be an inch or more in diameter than the tube so that the rubber will have to be stretched over them. This pitcher takes up little room in the toolbox, but is exceedingly handy in an emergency when the radiator requires filling on the road. Speeds Night Repairs ‘THE auto repairman often is confronted With the problem of extracting ball bearings that are located inside housings and cannot be driven from the opposite side.* Whe such parts are only a light driven fit, th ; be quickly removed by the use of the tool illus. Taceg or ey Can trated in Fig. 6. The hook is placed be. hind the part to be pulled out ang the sliding handle is used as a hammer. N AN emergency it is sometimes Value able for the owner of a Ford ear ty know that the nut that holds the front spring perch on the front axle will inter. change with the nut holding the reg wheel on either of the rear axles. If one of the rear axle nuts becomes stripped, it will not hold the wheel. By shifting the nut from the spring perch to the rear axle, however, and placing the damaged nut on the spring perch, the car still can be used, Cotter-pins are inserted in both nuts and if the spring perch does not seem secure, it can be wired temporarily.—G. A. L. HEN | the ; plunger of ’) a tire valve is no longer airtight, an emergency re pair often can be made by remov- ing the plunger and applying a drop of oil to the gasket seat. Not much oil should be applied, as it might get inside the tube and cause the rubber to rot. As the oil softens the rubber gasket, it will be necessary to replace the inside of _ the valve at the first opportunity. Fig. 4—Making a long tube patch COATING to protect the battery com- partment and the surrounding surfaces may be made of equal parts of wood tar and resin melted together and applied with a brush while warm. SUBSTITUTE THIS NUT IN EMERGENCY Fig. 7—Nut for axle CHEAP and effective method to economize gasoline consumption ina Ford or other light car is to drill and tap the intake manifold with a 7-in. pipe tap and install a small whistle valve. Sucha valve has a spring to keep it closed. 4 wire is run to the dash so it can be opened to let an extra supply of air in, espe when running smoothly over a good road on long trips.—JAMES ELLIS. AFTER soldering an auto radiator, it 8 good plan to cover the new work wi banana oil or shellac to close air holes. By Au the n taken many built but the | elabo: amat Sof succes of as body wire access good- often forma Ho" the re lem.

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Be. S. 5 ed with aces Or 188 and hey Can 0] illus. iced be. and the r, es valy. | car to 1e front ll inter. he Tear If one pped, it ting the ear axle, d nut on be used, 1uts and L secure, A.L. IN the Inger of Ive is no airtight, zency re- n can be y remoy- plunger plying a oil to the eat. Not il should ied, as it et inside be and 1e rubber As the tens the gasket, it necessary lace the of the t the first nity. JATING protect tery com- nt and rrounding s may be of equal of wood 1d applied rethod to :ption ina ill and tap 1. pipe tap e. Sucha closed. A be opened especially good road tor, it is8 work ir holes. POPULAR SCIENCE MONTHLY | Y, by) rks hop Arthur Wakeling, Editor Giving Wings to Your Speedster How to Improve the Racin By George Arthur Luers Automotive and Mechanical Engineer ONVERTING a Ford or § other light car into a sporty- looking speedster is one of the most fascinating tasks under- taken in the home workshop. How many thousands of speedsters are built each year cannot be estimated, but their construction comprises the greater proportion of really elaborate projects undertaken by amateur mechanics. So far as appearance is concerned, success usually rewards the builder ofasport car. A racy, ready-made body can be purchased, as well as wire or disk wheels and the various accessories that insure constructing a good-looking sport car. The difficulty often is, however, that the car’s road per- formance does not live up to its looks. How to add speed to your speedster is g Quality of a Light Sport Car Bae eee renerreetininannee ne the real problem when building a sport car. It also is the most interesting prob- lem. Whether you already have con- Properly remodeled, a cheap, light auto can be made fast and depend- able on the road as well as distinctive in appear- ance like the sport car illustrated. Note the alu- minum instrument board REMOVE MAGNETS AND CLAMPS TO REDUCE WEIGHT ABOUT 35 LBS REINFORCING FRAME IM OF FLYWHEEL ) ee OILTROUGHS \ __ a Sel heer (QE Ty REDUCING WEIGHT OF PISTON AND CONNECTING ROD WITH DRILLED HOLES INCREASING OIL LEVEL OF ENGINE PAN REAM OUT Va LARGER ‘ ’ Sw 0G SUBSTITUTE TRACTOR VALVE (1/4 LARGER DIA) EXHAUST MANIFOLD REDUCING o, Gj tus — ‘ “ SSTEEL PIPE =A VAHOLES’ yg» REDUCING OBTAINING FREE EXHAUST How to reduce the weight of engine parts, enlarge the valves, ‘Improve the lubricating system, and reconstruct the muffler structed a speedster or are planning to build one, it will pay you to make use of as many as possible of the fol- lowing suggestions in remod- eling the engine. On a fast highway you can hope to outdistance other cars only when engine con- ditions are just right. To get the necessary increase in engine revolutions, the engine balance, ignition, lubrication, cooling system, and all other factors must be designed and adjusted properly. About 75 per cent of speedsters are remodeled Fords. Since a Ford has four separate coils operated from =] a low-tension magneto, each coil | emits a series of sparks for each ex- | plosion in the cylinder. It is ap- parent that after the first spark ignites the explosion, the successive sparks are of no use. While this system is satisfactory for slow and moderate speeds, it will be seen at once that a multiplicity of sparking is not sufficiently accurate when the engine is turning over at 2000 or more revolutions a minute. A speedster normally is fitted with a starting and lighting battery. This leads to the use of a single spark system of ignition, which gives a single hot, live spark for each explosion. Such a spark can be timed accurately to occur at the correct point in the compression and it acts uniformly for each period of engine rotation. Equally good results are to be obtained with a high-tension magneto. A magneto of this type, with complete fittings, can be had for attaching to the timing gear in the front end of the motor or to the end of the camshaft after the regular roller commutator assembly has been removed. The low-tension magneto should be removed unless the coils are used for lighting purposes, when no battery is pro- (Continued on page 120) Where to Find This Month’s Mechanical Features The Home Workshop Pages 83 to 123 The Shipshape Home Pages 124 and 125 Better Shop Methods Department Pages 88 and 126 to 136

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A Folding iin "hy pera By A. Neely Hall Specialist on Handicrafts in the Home for several purposes, among which may be mentioned the shielding of the bed from draft from an open window and from glare of morning sunlight. It is an essential part of nursery furnishings, yet often is one of the last things pro- vided because of the cost. To the father handy with tools, making a screen is no trick at all. The framework of the threefold nursery screen in the photograph is of 1 by 2 in. strips, which can be purchased at any lumber yard. The panels are of wall- board, obtainable from the same source. Wallboard serves well for paneling, and is easier to obtain in wide pieces than wood, which usually must be veneered if wider than 12 inches. It is more desirable for nursery use than any textile because it can be enameled and thus made washable and sanitary. Number 1 of the mechanical drawings gives dimensions for the framework of the screen, and 2 and 3, details of the stiles and rails. Note that the strips are grooved to receive the edges of the panels; also, that they are mortised and tenoned. If you have no dado plane with which to make grooves, use a 14-in. chisel. It is A SCREEN is useful in the bedroom POPULAR SCIENCE MONTHLY April, 1935 creen for the Nursery Has light panels of enameled wallboard ornamented with rabbits Make the grooves at easy to cut them. least 3¢ in. deep. Coat the edges of the panels, the grooves, mortises, and tenons with glue, and after reinforce the glued joints assembling, A screen that is easy to keep clean with finishing nails. A child’s screen is more inter decorated with nursery figures, and it ; easy to apply these. You will fing hry able pictures in nursery books and maga zines, and you can enlarge a picture to the size desired by the system of squares as explained by the sketches of a rabbit in the panel diagram. First, make a paper tracing of the Dic ture selected, and draw parallel and vertical} lines across it, spacing the lines at equal distances. Make a set of similar but larger squares upon a piece of cardboard, draw the outline of the picture upon the large squares as it is seen upon the small squares, and the enlargement will pe an exact reproduction of the small draw. ing. Cut along the outline of the larger drawing, and use this cardboard pattern to draw around in laying out the picture upon the panel. With the picture or pig tures drawn in lead-pencil, fill in between the lines with black paint. Black auto enamel is excellent for the purpose. esting if Ordinary hinges may be used for hing- ing the frames of the screen, but they fold only one way. A better hinge is the double - acting type shown in 5 and 6. Notch the edges of the stiles to admit the flaps of the hinges. After fitting the hinges, remove them until you have fin- ished the frames. Two coats of flat white and one or more coats of white enamel should be applied. How the framework is put together, with mortise and tenon joints. Details of the wallboard panels, and a double-acting screen hinge Large Clothes-Rack May Be Built Cheaply 7° INSURE quick drying, a clothes- rack must be designed to allow the air to:-cireulate freely around the clothes. The rack illustrated is large enough to insure this and at the same time it is so built that it can be placed around the stove, hot-air register, or radiator. If only a few clothes are to be dried, it need not be unfolded fully. When not in use it collapses flat. In building one section of the rack, fasten one end of each horizontal bar or strip to one of the uprights with long, round-head wood screws. The other up- right is grooved at corresponding inter- vals so that screw hooks turned into the ends of the horizontal members may be placed in the grooves and bent to form a sort of screweye fastening. These screw- eyes are loose enough to act as hinges. As many sections as desired may be built and connected, as shown in the ac- companying photographs.—J. J. BYBERG. The clothes- rack ready for use and folded up to be stored away; how the joints are made A. eee it ¥ i i SCREW HOOK BENT TO FORM EYE | Pump Repaired with Rubber pees and others who depend ona well for their water supply often have considerable trouble because their pumps “‘run down” and have to be primed every time water is wanted. This trouble usu- ally can be remedied at practically no cost other than taking the pump apart. From a piece of old inner tube or patch- ing stock, cut a piece the same size and shape as the flap on the lower leather check valve. Attach the rubber to the under side of the valve flap with the bolt or screw that holds the iron valve weight. Be sure the rubber is as large as the flap. Then put the pump back. The rubber is more flexible than the leather, and sand will not get under it and collect on it. While this is a simple repair, it is surprising how well it works. Our pump gave us trouble for years at various times, but this repair ended the difficulty —CLYDE BRINDEL. i i i 4 eo... Be fe Ue eu srlC MM .lClCUr CU}

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hg if it is suit- naga- 0 the eS, a8 bit in e pic. rtical equal larger draw large ill be draw- larger attern victure oF pic- tween < auto

april, 1925 POPULAR SCIENCE MONTHLY 85 How to Give Home-Made Furniture that Finished “Professional”? Look After spending precious hours making furniture by hand, you naturally want to give it as beau- tiful a finish as possible. Surely the finishing should receive its share of attention, for a beau- tiful piece of furniture may be ruined if improp- erly finished, whereas any small defects are minimized if well finished.

The Johnson Book on Wood Finishing gives complete instruc- tions for finishing new and re- finishing old wood—soft or hard. It tells how to stain wood artis- tically—how to remove old paint and varnish—how to secure a beautiful enamel finish, etc. This book is the work of experts— profusely illustrated in color. It includes color charts—gives cov- ering capacities, etc. It is full of valuable, authoritative informa- tion on Artistic Wood Finishing. ‘ The coupon below tells how to get a FREE copy of this authoritative manual on a fascinating subject. JOHNSON’S WOOD DYE Johnson’s Wood Dye is for the artistic coloring of | Johnson’s Wood Dye is made in seventeen beautiful all wood. It is very easy to apply —dries in four shades, among the most popular of which are: hours and will not rub off or smudge—penetrates 123—Dark Oak 131—Walnut deeply, bringi t the beauty of the grain. eeply, bringing out the beauty of the grain 129—Dark Mahogany 126—Light Oak Johnson’s Wood Dye is a dye in every sense of * the word. It contains no finish whatsoever. Like 127—Brown Mahogany 124—Golden Oak most first class products it answers one purpose All shades may be easily lightened, darkened or only—it dyes the wood. A finish must be applied intermixed. Full directions on every label. Select over it—we recommend Johnson’s Varnishes or the shade of Johnson’s Wood Dye that you want Johnson’s Polishing Wax. and order it from your dealer by name and number. frrss":=**"-FREE—25¢ BOOK ON WOOD FINISHING-----------3

a Ask for a FREE copy of the Johnson 25c Book on Wood Finishing at stores displaying the sign shown atright. These ium cl Yhe -_ stores carry Johnson’s Artistic Wood Finishes and will be glad to show you wood panels—and answer questions on SERVICE PROPER how to properly finish wood. If no store in your locality can supply the Johnson Book — mail this coupon for a copy ay REATMENT —Free and Postpaid. OR FLOORS | LOODWORK ii NIU PPM PE Ss te So aN eek peels Me pl Es Du ot a nd FURNITURE =e = 3 JOHNSON | ARTISTIC wooD FINISHES CODEN DS ES ee Your Address... OHNSON ¢ SON City and State... S. C. JOHNSON & SON, Dept. ] P.S. S.4, F RACINE, WIS.

© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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86 POPULAR SCIENCE MONTHLY Stepping-Stones for Garden ; How you can build picturesque pathways about your home G "ecto are, much les made of con-_ used are: 9 by 9 in., 9 by + C es me 506% oo Pd im 7 ; Oe Gas. crete are much less expensive and _ 11 in., and 11 by 22 in. much easier for the home-owner These three sizes can be to make than a solid sidewalk. In addi- arranged in a large variety tion, they have the advantage of a more of combinations, with artistic appearance for garden pathways about 2 in. of sod between or walks between house and garage. The them. fact that so many architects now specify One form for each size stepping-stone walks in connection with is sufficient to produce a designs for costly residences is an indica- considerable length of tion of their decorative value and growing walk in the course of a popularity. few days, but if more Frost will not injure this kind of awalk, speed is ‘desired, two or for if the individual stones are lifted in more of each may be used. the winter, they will settle back in place The forms are made when spring comes. from pine lumber about 3 Slabs of several sizes make a more. in. wide, nailed to any attractive walk than if-only one size is sort of boards, or simply used. In the walk illustrated a pleasing nailed together and laid pattern has been obtained with only onsmooth ground. If the forms are laid three different sizes of slabs. The sizes on the ground, care must be taken to keep the framework down by driving “ pegs into the earth and nailing the wood to them. The mixture to be used for the lower part of the slabs can be one part of cement to four parts of coarse, clean gravel. Remember to mix the gravel and the cement thoroughly before adding water, and add the water in small amounts, being careful not to produce too wet a mixture. Now oil the forms and fill them to within 14 or 14 in. of the edge with the mixture. ‘‘Tamp’’ it down solid and run a trowel around the edges to force the larger pieces of gravel away from the boards. ; The work is now ready for the fin- ishing coat, which is made up of two parts fine sand and one part cement. ~ “4768 tepping.- stones made of concrete eens Marking length of form members In nailing the forms together let nails project so they which are made of 3-in.-wide strips can be pulled out easily when the concrete is hard Square the form and nail it to a baseboard Mix the cement and gravel thoroughly before adding water, then wet the mixture and turn it over and over until uniform in consistency. This mixing-board is the back piece of a piano box Oil the forms lightly with brush or rag to prevent cement from stick- ing. Discarded crankcase oil may be used for this purpose, if desired The correct con- sistency of the concrete is shown above. Avoid a sloppy mixture. After the forms are filled, the surface is smoothed with a wooden block, as at the left. A very smooth surface is not desirable, so do not do _ too much troweling This mixture may be colored to suit the maker’s taste and design by'the use of Venetian red, burned umber, yellow ochre, or almost any other inexpensive color, in powdered form. This color should be mixed dry with the cement and sand before water is added. Too much color will weaken the cement. When the surface has been smoothed with a wooden block, the sharp edges around the form can be rounded with a sidewalk edger, with a small trowel, or, in fact, with a homemade wooden tool. The slabs are left for one or two days until the mixture ‘‘sets.” They must be protected from the sun during this process and should be kept moist, particularly if the weather is hot. The forms are used again and again until a sufficient number of stones is made. When enough slabs have been made for the walk, a sketch should be made showing the best arrangement of their positions. The simplest way to lay them is to excavate as for a continuous walk of the same width and, after the slabs are laid, put pieces of sod be- tween the blocks. 3 More irregularly shaped stepping stones can be made without forms simply by excavating holes in the ground and filling them with congrete. 4 4 : 4 c é 4 r ‘

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Ping- $s made merete ‘iving z the lower art of clean rravel efore fer in ot to om to th the i and force from ie fin- f two ment. O suit he use yellow ensive color ement Too ent. othed edges d with rowel, rooden yr two They during moist, t. The n until made. 1 made > made of their to lay ‘inuous ter the od be- »pping- forms in the n crete. Apeil, 1925 EG URFAT OPN Whatever work you have to do, there is a Disston Saw to do it Disston Back Saw, No. 4—For accurate cutting of mitres, fine joints, or stock of small dimensions. £7 . \ tj } Disston Coping Saw, No. 10—For cutting scroll work, ornamental wood work, toys, = Tension of blade adjustable to each job. a a rn Cet TN aaa = Disston Nest of Saws, No. 3—Ten-inch key-hole saw, 14-inch compass saw, and 16-inch utility or pruning saw, with adjustable handle. POPULAR SCIENCE MONTHLY OUR first saw! When you choose it, you are setting a standard for the work you have to do in all the years to come. You need not be an expert when you go to buy your saw, for the carpenter has chosen for you. The Disston Saw, every- where, is “The Saw Most Carpenters Use.” The Disston Hand Saw cuts true to the line. It is true itself —smithed and tensioned on the anvil by a master of the craft. It cuts fast without bind- ing because it is ground right for clearance. Only a Disston craftsman can taper a saw blade to work like that. It seems ‘‘alive’’ when you use it, so easy is its balance. Only a Disston expert can give a saw such balance. And your Disston Saw will hold its edge: Disston makes the steel and gives it the Disston temper! Disston Saws, of Disston Steel, are the most widely used saws in the world. Me- chanics everywhere have learned what the name Disston on a saw means to them. “After 20 years’ use, my four Disston Saws are good for another 10 or 20 years. Some saws! The good old Disston—an honest saw for honest work.” —John J. Harris, Brattleboro, Vt. “T am still using a Disston Saw that was my father’s before me. It has been in use 65 years and is still good. I have used Disston Saws for 36 years.” —J. E. Harrison, Atlanta, Ga. “T wouldn't lay down my Disstons for any other saws on earth, and I have been using them for more than forty years.” —L. L. Loftis, Price, Utah. You will find the Disston Hand Saw at the _ nearest hardware store. Take it in your hand. Try its spring, its easy thrust and balance. Then make that saw your own! Ask Disston! Tell us what kind of work you are doing, in wood, metal, stone, ivory, rubber, leather, cloth, fibre or other material, and we will tell you what types of saws to use. Disston issues many books to aid the users of saws and tools. Henry Disston & Sons, Inc. Philadelphia Hardware dealers the world around sell Disston Saws, Tools, and Files DISSTON r(S} This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. 87 To the million young men who are buying their first saws ©

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POPULAR SCIENCE MONTHLY By Edward Kilburn Machine-Shop Superintendent OTHING is more condu- N cive to fast and accu- rate work than to have the proper tools within arm’s reach. This is especially true in respect to lathe work, which plays such an important part in every machine-shop’s output. “A place for everything and everything in its place” is, in- deed, a maxim particularly ap- plicable to the machinist’s trade. The great number of small tools and appliances cannot be used to best advantage of they are not handy. The accompanying _illustra- tions show how to provide facilities for properly taking care of all the small tools and accessories used in connection with lathe work. The rack is particularly useful where it often is necessary to re- move the toolboard (if one is used) when doing full-length work on the lathe. The tool cabinet is supported by a frame made of pipe, pipe fittings, and flat and angle steel plates, joined together by welding. The stationary portion of the frame is bolted to the back of the lathe- bed near the tailstock end. The other part is adapted to swing upon the sta- tionary portion and carries at its upper | = , ap luaBee The tool rack and framework end a cabinet with suitable drawers for cutters and other small parts. The lower flat or table portion of the cabinet is used for lathe tools; the upper board to hold lathe centers, tailstock chuck, and the like. DRAWERS ~~ H | HANDLE =? 0 a 7 How the frame work is made The mechanism of the device is so arranged that when the cabinet is in posi- tion over the lathe-bed, it may be lowered to rest firmly on the bed. When it is desired to remove the cabinet from the bed, the cabinet is raised and swung around out of the way. A ball bearing is provided at the lower end of the frame to make its operation easy, The mechanical diagram shows clearly the construction of the elevating device and bearing. It will be noticed that there is a central threaded rod, At its lower end this bears on a cross bar, which rests on the top of the ball bearing. The bar is located in a slot in the central hollow portion of the swinging frame. Screwing the nut A at the top of the bar against the upper flat bar B raises the frame and with it the cabinet. Releas. ing the nut lowers the cabinet. The nut A has a flange or enlarged lower portion, which bears upward against the bar B. The main or upper part of the nut, which passes through B, is fitted with a handle. This device is much more convenient than a stationary cabinet, which must be removed to the floor when long work is placed in the lathe. As soon as it is on the floor, a cabinet becomes nothing more than a stumbling block for every passer- by, and the chances of tools being lost or damaged are greatly increased. Spring Threading Tool O OVERCOME the shortcomings of certain commercial spring threading tools, which have no provision to prevent them from springing sideways or parallel with the axis of the screw being cut, the tool illus- trated was devised. It is prevented from springing sideways by the Detail of plate, B, shown tool-holder directly beneath the spring bushing. This is keyed and screwed to the shank, A, and has a slot in its top edge that engages a keylike ex- ‘ tension or lug, C. Bushings are inserted as desired, to in- crease or decrease the spring of the tool.— CHARLES KUGLER, Philadelphia, Pa. ON’T fail to turn to pages 126-136, where you will find the continua- tion of the Better Shop Methods De- partment.

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7 Tame gram ction and 1 that 1 rod. 3ona 1e top bar is entral inging A at st the frame ‘eleas- inet. ge or which bar B, which andle, enient ust be rork is t is on y more passer- lost or l ings of eading revent yarallel Yetail of 501-holder ved and a slot in like ex- i, to in- e tool.— Pa; 126-136, ntinua- »ds De- Starrett POPULAR SCIENCE MONTHLY Apprentice Set No. 901 You'll use the Starrett Tools you buy today for the rest of your life. Ten years seems like a reasonable length of service for a Precision Tool, yet any veteran machinist will show you Starrett Tools which he has used twice and three times ten years. It’s all in the way Star- rett Tools are made. Parts are cor- rectly proportioned. The finest steel the market affords goes into these lifetime tools. The workman- ship is unexcelled—a _ character- istic which is obvious when you examine a Starrett Tool—and is always evident in its lasting accu- racy. Starrett Apprentice Sets (Nos. 900 and 901) give you the tools you need to start — and tools you'll always need. Sold by first-class hardware stores everywhere at a price you can afford to pay. Write for Starrett Catalog No. 23 “W’”’ describing the uses of 2200 Fine Precision Tools FREE. > THEL.S. STARRETT CO. World’s Greatest Toolmakers Manufacturers of Hacksaws Unexcelled Starrett Tapes—Standard for Accuracy 7550 ATHOL, Mass. The Starrett Set for Apprentices and Students comprises the following Precisio spihed wood tool box: 6-inch Combination Square No. 11 complete, . No. 117-B, Center Gage No. 390, 5-inch Divider with Spring Nut No. 77, 6-inch Outside 6-inch Flexible Steel Rule in-Pocket Case No. 320, Caliper with Solid Nut No. 79, 6-inch Inside Why do the Crack Machinists Advise the Apprentice to start with Starrett Tools n Tools neatly cased in a substantial and nicely Center Punch Caliper with Solid Nut No. 73. And the Starrett Book for Machinists’ Apprentices (Vol. I), 184 pages that show “‘how to do it.” © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See pago 25.

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Look for on the head T’S definite assurance that the hammer with the looks and perfect ‘‘hang”’ has in addition a quality and toughness that makes it good for years of hard service. Most experienced tool users can tell a Maydole Hammer even without looking at the name. It has a distinctive char- acter that has been developed and enhanced throughout the 82 years devoted by its makers to perfecting the hammer. Pick up a Maydole and you'll find it has a “‘hang” unlike any other hammer—most carpenters, machin- ists and other me- chanics like it better. Ask your hard- ware dealer to show you a _ carpenter’s, machinist’s or other | with strokes made | the whole length “D. MAYDOLE” type of Maydole Maydole Ball Pea Hammer. You'll see ute: tie Hammer . Head i, of press the difference. org a imper~ . Sd For the persicae Write for useful perform. Handles DOCKet handbook 23 clear, sec ~atinere oe “B.” It’s free. dried for years. The David Maydole Hammer Co. Norwich, New York 7050 Surface planing of the board, if possible (above). If board is wide, “cross plane’”’ it first; then start at one edge, let- ting each shaving partly overlap the previous one until the whole surface is covered. Re- peat, working back to the first edge Marking to length (at right). Lay rule on_ surface, locate knife at correct point, then move square up against knife. For accurate work, draw lines all around the board } | POPULAR SCIENCE MONTHLY Sawing board 1/16 in. beyond knife line to allow for truing the end with the plane by the method previously used Testing with square (at left). The end must be tested both from the broad sur- face and the long edge. Hold handle firmly against surface and let square down slowly. The last plane stroke must be right across Expert Shows You His Own Methods By Emanuel E. Ericson, Noted Manual Training Authority Testing the surface with edge of plane against the light (above). Also test from corner to corner to detect twist or “wind.” If board is large, this is done on the bench, using a straight edge, if plane is not long enough Planing end (at left) after one broad surface and one long edge have been planed. The long planed edge is toward the worker, Note that one corner is chiseled off to prevent wood from splitting Gaging for thick- ness (above). Hold the gage firmly against the wood and tilt bar for- ward. Mark both ends and edges. When planing put rough end against the bench stop j Marking to width when a board is too wide for the gage. When the edge is planed, the chiseled corners disappeaf © This seal’on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. ge MB oe Pri ges Bere,

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B38 eee @ on k- ld ly r- caRY ES POPULAR SCIENCE MONTHLY N THE attractive living room above, Upson Ss Board has permanently renewed shabby walls emis and ceilings. UPSON And aside from its use for walls and ceilings, BOARD Upson Board has 100 uses around the home. a. Its easy workability makes it ideal for making wardrobes, photographic dark rooms, cabinets, doll houses, wastebaskets, lapboards, tables, toys and countless other useful articles. It will pay you to keep a few panels in your home workshop. Mail the coupon for samples and details! ee a ee Oe a a a THE UPSON COMPANY ’ 427 Upson Point, Lockport, N.Y. Check here and mail with Checkhereandenclose2sc # 5scif you want Upson if you want blue print. J samples and literature. What kind of room?............00+ P New or remodeling ?.........-...-.+ 1 SMRPABM MRIS AD cc seco sc cscs ay gsassasavacy dcacdieS acu cedancsenccsisarsscusesexsnets Leesewewwe ewe ew ees ee eee ee last- a wall that successfully vs Hibadadibeda gs s resists heat=-cold wee ws wy \ars-oisture “time i pe NINE out of ten homes, investigation shows at least one cracked, shabby plaster wall or ceiling! Now there is a sure, quick, easy way to transform such a room. Upsonize! Apply big, sturdy panels of Upson Board right over the old plaster—in new construction, direct to studs. Then, appropriate wood trim, a coat or two of paint—and your room is finished. Upson Self-Clinching Fasteners, a patented and exclusive Upson innovation, eliminate ugly nail marks—the big objection to ordinary wallboards—by anchoring Upson Board securely from the back. The nearest-perfect wall material! Conclusive tests have proved the superiority of Upson Board. In one of many dramatic tests for strength, made by impartial engineering laboratories, weights were dropped from several heightsupon specimens of different wall materials. Upson Board withstood an impact of 40% to 70% more than the other fibre wallboards tested, and nearly 150% more than plaster-filled boards twice as thick. Jars and blows that would ruin ordinary plaster walls have little or no effect on Upson Board. In another impressive test, Upson Board immersed in water for a given length of time gained only 14 ounce to the square foot. Gypsum-filled board exposed to the same test increased nearly 14 pound to the square foot. Other wallboards were found to absorb nearly twice as much water as Upson Board. The ordinary leak has little or no effect on Upson Board. A wonderful new plan service! Ask your lumber dealer to see the amazing new Upson Blue Book—the most complete plan service ever offered for renewing and beautifying walls and ceilings. If he hasn’t it, send us his name and 25c, and we will mail you full-size blue print with complete directions for Upsonizing any room. (State kind of room and whether new construction or remodeling.) THE UPSON COMPANY 427 Upson Point —_ Lockport, N. Y. PROCESSED Genuine Upson Board has the famous Blue Center cS] This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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‘ | HE new Millers Falls glass ‘i cutter wheels cut as steel wheels never cut before. They are hard, sharp, uniform; the edges last. They are. right. We've been making glass cut- ters for 45 years. With all that experience, We putin morethan a year of intensive plugging to develop our improved wheels. The wheel has always been the weak spot. We tried many steel alloys, different heattreatments. Each new lot of wheels was tested rigorously. Now we say they’re right, be- cause we have proved it to ourselves. The Millers Fails name on them proves our con- fidence to you. This is No. 7 Improved— Mie, single wheel; easy grip handle, enameled red, This is No. 300 Improved— six perfect wheels in tur- ret flush with frame. Wheels protected from injury by patented fea- ture of cutting arbor in- tegral with turret. Easy grip handle, enameled hardwood. Millers Falls Improved Glass Cutters with the new long- life, fine-cutting wheels. Special alloy steel wheels; hard- ened byspecial proc- ess; uniform; lasting. They make a deep, clean cut. Eight styles. © MILLERS FALLS COMPANY Millers Falls, Mass. 28 Warren St. 9 So. Clinton St. New York Chicago Manufacturers of Mechanics’ Tools, Hack Saws and Automobile Tools MILLERS FALLS TOOLS POPULAR SCIENCE MONTHLY SSS Ludenions New a Toys Made Entirely of Wood By Charles M. Miller Asst. Supervisor of Manual Training, Los Angeles City Schools ANY methods of building new and interesting rabbit toys are suggested in the accompanying illustrations. With slight modifications some of the mechanical movements could be used effectively on other animal forms. The edges of toys cut with a coping- saw, such as these rabbits, should be square. Whether they are filed or sand- papered, or both, the edges should not be rounded, as is often done. The back legs, when movable, operate in unison. Usually they are connected below the body by means of a small dowel through both feet. Among the many mechanical move- ments possible, that of the rabbit shown in the photograph is perhaps the simplest. The form is l%-in. thick wood. The front wheels are glued to a 14-in. dowel that passes through a LY) 5/16-in. hole in the EE front feet. Small but- ' ( ton molds are slipped up close, but not too Ks tightly, against the sides of the feet to pre- RABBIT , RISES ‘._ HIND LEGS NAILED TO PIVOTED PUSHING FRONT LEGS HANDLE TWO-PART BASE |i proved by painting it with characteristic markings, some of which are suggested at the bottom of the page. Four movements a little more compli- cated than the Peter Rabbit toy are shown in the drawings of Fig. 2. In the first one, the rabbit raises his front feet through the action of a cam on the SHEET- METAL HINGE FOOT RACK Fig. 1. Simple rab- bit toys cut out with a coping-saw rear axle, which pulls a_ string at- tached to the tail. BASE STRIP PIVOTED FRONT LEGS At the same time another string, which runs from the baseboard up through the front of the body and the head to the ears, raises the ears at the end of the up- ward movement of SCROLL- SHAPED WHEEL BEARINGS CAM ON AXLE Fig. 2. Four methods of giving a toy bunny a lifelike hopping mo- tion as it either is pushed by a handle or pulled along the sidewalk vent the axle from slipping from side to side. The rear axle is the same except that the wheels are larger, in this case 3 in. in diameter, and closer together. The rear wheels are fastened to the axle about 34 in. off center; this gives a jumping motion (Fig. 1). Peter Rabbit in this particular toy has a red coat with a black collar. The ap- pearance of any rabbit toy can be im- the body. Shown at the right of this is a method for making a bunny hop. A wooden cam glued on the rear axle moves up a hinged board that in turn pushes up the hind feet. A third method provides for raising the hind legs with a string and cam and pulling them back with a spring. This toy operates well when pulled; the others are more certain in their action when pushed. In the fourth example the cam’s motion Is transmitted through two levers mounted on a shaft. rIS} This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. sd Wher “H. e BLA

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When you see a “Hex” think of BLACKHaWK! Save Your Knuckles O OVER every bolt and nut, from motor to rear end, with an ever-useful set of Blackhawk ‘“‘Q.D’s.”’ There’s a socket to fit every job, without ever slipping off—and a handle to give you just the right reach and leverage. Whatever make or model of car you drive, your dealer can supply you with a selected “Q.D.”’ set—especially de- signed by Blackhawk engineering for your particular car. Extra husky handles with comfortable grips and sturdy broached sockets—exactly 1/64’ oversize—tougher than any nut they will ever meet. You will like the rich, dur- able, all-black finish that’s baked on. See your dealer. Have him show how simple home repairing is with a Blackhawk “‘Q.D.” set. If he can’t supply you, write us direct. Made and Guaranteed by AMERICAN GRINDER MFG. CO. Dept. L, Milwaukee, Wis. (Also manufacturers of Blackhawk Water Pumps for Fords)

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For your radio: Helps you build and keep up your set. For your tools: Better than a stone for sharpening knives, axes and garden tools. For odd jobs: Files everything from wood to metal. With this file you can do any job NY man who likes to work with tools needs this new and better file—The Plumb All-Work File. The handle, forged as part of the file, fits your hand, gives you perfectcontrolof thestroke and makes filing easy. No handle to buy— no handle to lose—no handle to turn in your hand and ruin your work and temper. The sheath protects the teeth from rust or injury, fits your pocket and is fine for your tool ~ol File is 10 inches long, %inch wide—just the size that ismost ~~ [PLUMB DOUBLE-LIFE All-Work’ File with sheath (* Trade Mark Reg. U.S. Patent Office)

It has two faces; double cut (coarse) on one side for fast work, single cut (fine) on other side for a smooth finish. Two files in one, with forged handle and sheath. For your pocket, your tool kit, your shop and your car. 3 5¢ " iy dealer’s or by mail (40c West of Rocky Mts.) Don’t put off getting this file, just the one you need for every kind of work. The better hardwaremerchants now have the Plumb All-Work File. It’s a pleasureto supply you if your dealer can’t. Just send the price (stamps will do) andthe All- Work File will come to you by the next mail. FAYETTE R. PLUMB, Inc. 4812 James Street Philadelphia PLUMB |\ DOUBLE oe BE Hammers Hatc! Hatchets / Files Sledges Axes

POPULAR SCIENCE MONTHLY

By Edward E. de Lancey HIS is the second of a noteworthy series of railroad model- making. It explains the general principles of constructing motor-trucks for the beginner articles on simp lified whose tool equipment is limited. HE accompanying illustrations show the construction of a motor-truck. They indi- cate the method of mounting the motor, the gearing, the swing plate, shoes, and other essential details. | The trailer truck is a dupli- cate of the motor-truck, but or gearing. it must have its | own pick-up shoe and _ per- haps a separate return current without motor However, brush on one axl You will have to buy the following supplies: 1 pr. bevel gears, 16 and 48 fect ree larger gear usually spectively. The takes a 14-in. axle. one, ascertain the boring 2 sprocket wheels “ladder”’ 4 pr. 2-in. Have the

flanges rounded e. For the diameter armature shaft with a drill gage and use the indicated size of drill for re- with 12 type sprocket chain to fit wheels (preferably spokes), fitted to axles to a 2 14-in. projecting 5/16 in. beyond the faces of the wheel bosses. inside and out and the treads

smaller of the in. of with Building alanenveuie for a Model Railway gage, and having journals qa

Views showing gen- eral arrangement of motor-truck parts. Compare with the simplified construc- tion shown below

polished (Continued on page 101) > BOLT RECESSES | , - ~ f — COUNTERSUNK {ff Ye JOURNAL | BRASS BEARING AXLE BOX | ELECTRIC MOTOR Vg" OL HOLE =e 5 , CENTER LINE OF SHAFT “axe BRASS STRIP | Byles y ase WHEEL 2"DIA. UPPER TRANSOM 2x12 X3% MOTOR BEARING > Vi TREAD BABES LOCOMOTIVE = 7A va x\ie BRASS 4 == ~ ey ROUNDED ays OR wen BASE ay L/BOLTS AND ies tema ae + eas —

= —- “LOWER TRANSOM Ww XVEX3

V YANGLE Ss SIDE FRAME. TAPPED

SPRING mate 6

PICK- UP SHOE TO THIRD ® RAIL So : 3 a Space al es i | {Oo 203 o } . or 8 Ng DRILL OP AND BOTTOM OF SIDE FRAME ' 4 SE ee ee ee ae ee LOT; Oi; Oi: Oj: Oii:Py Di: Oi OF TOP OF AXLE-BOX STOCK t 5 6

{i th PRILL \\! EPERED i | ae R Mn

ae %, taal

“STOCK

PICK-UP SHOE TO THIRD RAIL” SPRING PLATE 8 X% ANGLE SWING STRIP CURRENT RETURN SHOE VATREAD

Fig. 1—Side elevation of the motor-truck. Fig. 2—Bevel gearing, sprocket, and section through the journal box. of spring plate and springs. Fig. 3—End view. Fig. 4—Part plan view. Fig. 5—Detail Fig. 6—Method of laying out brass boxes and side frames ee ALTERNATIVE CONSTRUCTION

© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS

See page 25. Ap

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POPULAR SCIENCE MONTHLY oe Satisfaction ee oe Reliability (Eastern Standard Time) For real radio enjoyment, tune in the “Eveready Group.” Broadcast through E CO nN O IN y stations WEAR Prrldcne WGAE Pion You need three things in radio “B” Batteries— till cll MB coso0 3 satisfaction, reliability and economy. You get them all in Eveready “B” Batteries. Satisfac- tion, because they produce all the current needed by your tubes, giving you the maximum results of which your set is capable. Reliability, because you can depend on them to work at full power. Economy, because they long maintain their strength, and because they are low in price. Advances in the art of battery manufacture make Evereadys last longer than ever. You actually get much longer service for your money. There is an Eveready Radio Battery for every radio use. Buy Eveready Batteries, Manufactured and guaranteed by NATIONAL CARBON COMPANY, Ine. New York San Francisco Canadian National Carbon Co., Limited, Toronto, Ontario EVEREADY Radio Batteries © -they last longer Eveready Columbia Ignitor Dry Cell Sa Battery No. 766 22%4-volt izontal Price a ae $2.00 No. 772 : 45-volt i Large Vertical Price $3.75 No. 771 Battery improves quality, saves “> ’ Batteries Price 60c IS] This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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A Necessary “Tool” For Your Workshop OR the man or boy who has a home workshop, Lee Union-Alls are a handy “tool” to have about. All that is necessary when you want to get busy is to slip into them and start your work. They cover the body from head to foot and can be worn over other clothing. They save clothes, also. And they save time where the hours for such work are limited. Wear Lee Union-Alls, the original one- piece work suit, worn by thousands of mechanics, shopmen, garage workers and industrial workers. Lee Union-Alls are quality-built—close-woven cotton fab- tic, riveted rustproof buttons, reinforced strain points—fully guaranteed to give satisfaction. They give solid comfort, long wear, and are neat in appearance. Accept no 'substitute—look for Lee onthe buttons. Thousands of live dealers sell Lee Union-Alls. Ask your dealer today! LeeUnion-Alls Kansas City, Mo. Trenton, N. J. South Bend, Ind. Minneapolis, Minn. San Francisco, Cal a= ~~ / = WSS Lee Overalls and Work Shirts are other items in the famous Lee line. ey are quality-buile, also. [The POPULAR SCIENCE MONTHLY April, 1925 "How to Re- Saas Your Old Chairs | The use of machine-woven cane—Steps in weaving the strands by hand basement’ there are probably one I: YOUR attic or By William T. Weld © and plane or scrape have been discarded Shopwork Instructor, or more chairs that Central High School, Peoria, I1/. the sides of it until jt makes a fairly tight fit in the groove. Now make three because the caning of bot- tom or back has_ been broken. To put chairs like this into use again is not nearly the difficult task that you might imagine: You can repair such chairs and at the same time spend several pleasant hours in your own workshop, or even in the kitchen. If the chair originally had machine-woven cane, you will notice that all the edges of the cane are held in place by a strip of reed or splines A seat that requires little. Meanwhile pour or or four wooden wedges for holding the cane in place temporarily. They should be from }4 to 2 in. wide, 6 in. long and tapering from 3/16 to 4% Hot cabinet glue is beak i. gluing in the spline, but a small can of first-class liquid glue placed in hot water until it is quite thin will serve nicely. Now for the caning itself, Soak the cane in lukewarm | water for two or three min- | utes to soften the fibers a embedded flush in a machine-woven cane spread the glue in | groove. If the chair WOODEN PEGS the groove and | is round, first locate AIDEN SIL along its sides, using | | a end of this _ LLIN S = ° a thin, narrow stick | sie _ = ( # 1 : orasmall brush. | or a small sharp ° ° screwdriver between ° : E LACE the moist- | theendsofthespline | = i 8 ened cane over | and start lifting it | ° ee e9Ke ° ° the chair opening | = of its on i = with the smooth or | ace a sma a glossy side upper- | block as a fulcrum AIDE HI. tS most. Arrange the | between the chisel Le x} strands exactly par- | and the chair rail or 0 J} allel with the front | frame and gradually pry up the spline. Square seats usually have four splines mitered at the cor- ners. Clean out the groove with the chisel followed by alittle hot water applied with an old toothbrush. EF THE chair needs refinishing, attend to it now. At Diagram showing the simple steps: by cane parallel to the least the chair which a hand-woven chair seat is made front and rear rails. should be washed thoroughly with soap and water to | which has been added a little ammonia. Machine woven cane from 10 to 18 in. wide may be purchased by the lineal foot at almost any upholsterer’s supply house, and some local furniture dealers carry it in stock. Your piece should be about 2 or 3 in. larger all the way around than the opening in the chair. Both the open | and the closed mesh, or matting, may be bought at about the same price. If you have broken or split the reed | spline while removing it from its gr-ove, | buy a new one. The size is standard and | it comes in lengths of from 8 to 12 ft. Cut off a piece several inches longer than the total cineca meneneee for your chair r| and rear edges of | c| the opening. Let the | S| surplus material ex- | v m, tend equally around | 5 all four sides. | Beginning at the | back, drive in one wedge, forcing the | cane down into the | groove. Do the | same at the center | of the front rail, be- | ing careful to keep BINDING CANE” 6-7 CHeDII the strands of the Repeat at the sides. With a larger wedge or a caulking iron drive the cane tightly into the groove all the way around. If there are any rounded corners, do these last with a narrow wedge. Your cane is now in place, but the outer edges stick up beyond the sur- | face of the seat. Take a sharp chisel or a heavy knife and, working from the inside, | cut off the surplus about 1/16 in. below | the surface of the seat. Take great care not to injure the wood. rs Some workmen prefer to drive the | spline into place first and trim off the edges of the cane by cutting carefully against the spline just before it is driven in tightly flush with the seat rails. Remove each wedge as you encounter (Continued on page 117) — rIS} This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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om, ret | he | of ed ‘ite elf. rm | \in- | 8 a | or | in | and | sing | tick | | vist | over | ning | h or | per- | the | par- | ront | s of | t the 1 ex- | | ound | ; the | one - the | o the | the | enter | 1, be- keep f the ‘o the rails. sides. | ; g iron | ve all | unded arrow e, but e sur- | el or 2 | inside, | below | it care | re the | ff the refully driven ounter “My wife said all radio sets “A strong sounded local sta- tion near us monopo- lized the air until we bought a LIBERTY Sealed Five.” ‘mechanical’ until she heard the LIBERTY. That’s why we bought 9 one. qq ang All five tubes are kept ‘matched’ because each tube is controlled by a separate rheo- stat. That gives pure tone. extremely selective. You need no verniers on these large dials. Owners of the LIBERTY Sealed Five are never without excellent entertainment. LIBERTY _ is POPULAR SCIENCE MONTHLY Delivered Scaled LIBERTY IS built for the Future a 7X } wir. i WKAQ “J installed one of your Liberty Five radios in my home last week and the first three nights I operated this machine I pulléd in the following stations: WCAP Washington WCBD Zion PWxX Havana WCAE Pittsburg KDKA E. Pittsburg KHJ Los Angeles WJZ New York City WLW _ Cincinnati WBZ Springfield, WMAQ Chicago WSAI Cincinnati Mass. WKAQ San Juan, P. R. WOS Jefferson City WMH _ Cincinnati WFAA Dallas WSB__sCqAAttianta WTAS Elgin, Ill. KFI Los Angeles KYW Chicago WHB Kansas City WTAY Oak Park, Ill. WWJ Detroit WDAF Kansas City WEBH Chicago WCX Detroit WOR Newark, N. J. WQ]J Chicago WOO Philadelphia WHAS Louisville WLS Chicago WIP Philadelphia WTAM Cleveland 2XBJ New York City WEAF New York City WJAX Cleveland WREO Lansing, Mich. WOC Davenport WGY Schenectady WHAA Iowa City WGN Chicago XG WBAP Fort Worth WCAL Northfield, Minn. WRC Washington WHN New York WLBL Stevens Point 8 Willard Test “I think the above test is remarkable inasmuch as I was not familiar with the operation of the set. Might also state that my residence is not located in a very desirable spot for reception but nevertheless the above stations were received in a very clear tone and with plenty of volume on the Loud Speaker. “J wish you all the success you deserve with this wonderful set. “Yours very truly, —100 (Signed) M. E. Mogg, President, less accessories for LN.V-E-S-T in a LIBERT LINTON CONSOLIDATED COLLIERIES COMPANY, this 5-tube tuned Radio Frequency INDIANAPOLIS.” receiver in beauti- ful two-tone solid Sealed Five 6 Manufactured by walnut cabinet. LIBERTY TRANSFORMER CO., INC. 555 NORTH PARKSIDE AVE., CHICAGO © This seal on a radio or tool advertisement signifies the approval of the INSTITU TE OF STANDARDS. See page 25.

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wu! 2 a In Steel Handle—Eight sizes from 6 in. to 48 in. In Wood Handle—, 8, 10, 14 in, sizes. A Bis Time And Money Saver ERE are the main reasons why most skilled mechanics, radio fans, householders and handy men demand the TRIMO PIPE WRENCH and will accept no other. Having a rugged steel frame that WILL NOT BREAK, the brutal strength of the TRIMO guarantees your personal safety when hazardous or tough jobs have to be done. You can make a TRIMO last for many years because its IN- SERT jaw in the handle can be renewed at small cost when worn. Handy NUT GUARDS that keep the wrench adjusted, make the TRIMO an ideal tool for working in close quarters. At most hardware, plumbing and mill supply stores. TRIMONT MFG. CO. Roxbury, Mass. America’s Leading Wrench Makers Jor nearly 40 years POPULAR SCIENCE MONTHLY How Vow Gon Co MR. MURRAY, whois wellknown to readers of POPULARSCIENCE MONTHLY for his articles on the construction of ingenious novel- ties, 1S an ama- teur magician of established repu- tation and an ex- pert on sleight- of-hand illusions. His next article will tell how to make a palming device for cards. SR RL Ft Se Se es nstruct Easily a Trick Savings-Bank for Coins By Kenneth B. Murray bank is shown in Fig, 5. -The secret of the trick bottom is re. vealed in Fig. 4, which shows how two of the bolts on the bottom are faked. Two of the bolts act as pivots on which the bot- tom can _ swing; they are real. The other two consist of the bolt heads only, soldered in place. When the secretly Fig. 1—The parts needed for making the bank T IS -practically | the impossible for the uninitiated to open bank illustrated, simple as its construc- tion is. It can be made at she small expense from et steel and brass bolts. The parts necessary are shown in Fig. 1. hinged bottom of the bank is closed, the short projecting ends of the fake bolts catch into corresponding indentations in the bottom, or, better still, although not shown in the accom- panying photographs, into holes the same as those for the real bolts. Being a tight fit, the bottom is held by the short bolts securely and it is necessary to exert con- siderable force with the thumb, as shown in the upper illustra- tion, to open the bank. A coin slot, of course, is made in the top. Fig. 2—Fastening a side and an end piece with bolts The wide side pieces for the bank are 4 in. square, while the narrow side pieces and the bottom and top are 3 by 4 in., with Fig. 4—The bank open flanges of ap- proximately 7/16, in. Figures 2 and 3 show how the bank is put together with a screw- driver. Spe- cial note should be made to fix the brass bolts firmly after each is fastened in place by hammering it as one would clinch a rivet. It must not be possible to un- screw the nut from the bolt. The completed Fig. 5—Ready for use Fig. 3—Putting the top in. Note how the bottom is pivoted on two bolts Waxed Cloth Sometimes Is Useful as Glass Substitute | gwd ning of glass for the windows of poultry houses, hotbeds, cold frames, and even storm doors, it is possible to use cheesecloth or other light weight white cloth treated with paraffin. shaved very fine with knife or block plane, is spread on the cloth and pressed into it with a warm but not hot electric iron. It is important to use plenty of paraffin and to cover only a small section at a time. The cost of the waxed cloth is about one-half that of ordinary glass. while the cloth does not admit the light like glass, it is transparent enough so that newspaper type can be read through It. —CLAUDE O. Soots, North Salem, Ind. The wax, |: a © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. M nd

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April, 1975 POPULAR SCIENCE MONTHLY

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E | \ \ Mii om — (CS <5 = .* / . a, ae a it 7 ) / , ay E @ y al ib ae Music Master Resonant Wood Insures Natural Tone Quality Model VI, 14” wood bell $3) Model VII,21" wood bell $3 5 Connect Music Master in place of head- phones. No batteries. No adjustments. Prices of all models slightly igher in Canada —Its True Significance HE advent of Music Master sounded the death knell of the mere loud speaker.” For it transformed the radio receiving set into a musical instrument—a triumph of re-creative art. Two years ago Music Master’s full voiced volume and characteristic tone qualities heralded the New Era of Radio Art. It made possible the re-creation of supreme Music, Song and Speech, in the wonderful stellar programme now an established feature of American nation-wide broadcasting. Music Master does more than reproduce—it interprets, it re-creates—it transforms mere radio receiving into artistic enjoyment. Music Master has been imitated often, but without success. Music Master remains the unsurpassed musical instrument of radio—and there IS no substitute. MUSIC MASTER-—the Ultimate of Artistic Radio Re-Creation Music Master’s precision instrument is the acme of scientific perfection. Music Master’s tone chamber of heavy cast aluminum is a marvelous mold of sound without distortion. Music Master’s amplifying bell of resonant wood gives to every sound its full, vibrant qualities and natural and lifelike characteristics. Music Master’s manufacturers hold that every purchase of their product carries with it an implicit pledge of unreserved and unconditional protection. Back of your dealer’s full and unfailing service stands the Music Master Corporation to guarantee its products direct, to anyone, anywhere, at any time.

Model VIII, Mahogany Cabinet with “full-floating” wood horn $35 Music {Master Corporation Makers and Distributors of High-Grade Radio Apparatus Tenth and Cherry Streets Philadelphia Pittsburgh Canadian Factory: Kitchener; Ontario

Model V, wood bell, Metal $18 Cabinet, Mahogany finish Chicago

© This seal on a radio or tool advertisement signities the approval of the INSTITUTE OF STANDARDS. See page 25.

tsi in OTe ei . oe oer a ee

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An awkward job made easy by the “YANKEE” Ratchet Tap Wrench E had to tap a thread in the transmission case for a mag- neto plug screw. Without a “Yankee” Tap Wrench he would have been com- pelled to remove the coil box. But the “Yankee” Tap Wrench made this unnecessary. He just pulled the sliding cross bar out to end position, where his hand could move freely; set the Ratchet Shifter, and tapped the hole quickly and easily. Three adjustments. Right-hand Ratch- et, Left-hand Ratchet and Rigid. Knurled finger turn at top quickly starts or backs out taps. No. 250—Length 314 in. Chuck diam., 34 in. Holds up to 3/16 in. taps. No. 251—Length 5 in. Chuck diam. % in. Holds up to 5/16 in. taps. No. 1251—Length 13 in. For jobs needing long reach. Otherwise same as No. 251. Some Other ‘“‘YANKEE”’ Tools Spiral Screw-drivers Quick-Return Spiral Ratchet Breast Drills Screw-drivers 4 | Leteus mail this Book to you FREE! If you like tools you'll want this FREE “YANKEE” Tool Book Shows every “Yankee” Tool, and tells you all about them. Write for your copy today. “‘YANKEE” on the tool you buy means the utmost in quality, efficiency and durability. Dealers Everywhere Sell ‘‘Yankee’’ Tools. NortH Bros. Mee. Co., Philadelphia, U.S. A. “YANKEE” TOOLS Make Betliv } POPULAR SCIENCE MONTHLY Easily Made Cigar-Box Novelties HE picture-frame and candlestick illustrated can be made at home more easily than almost any other piece of woodwork. It is not necessary to copy either design exactly; the method can be used with endless modifications and for ornamenting many objects, including boxes, bookends, stationery racks, inkstands, sewing trays, and the like. divisions must come out even Cut the notches with a thin, sharp knife, making them clean and square. The file or sandpaper is not used op them. Mark the places for the blocks on the frame, heat the pieces slightly, if convenient and glue them in place. Hot animal glue is quick-drying and satisfactory, but a good liquid glue will serve the The tools needed are few— a rule, a pocket-knife, and a piece of sandpaper, and, if available, a small plane, a square, a coping-saw, and a file. All the wood is taken from empty cigar boxes. Boxes made of Spanish cedar (a red wood that looks like mahogany) will produce the best effect, but any kind of wood can be used and stained the desired shade. A combination of various colors purpose. Liquid glue is han- dled more easily when heated. While the glue on the surface of the frame is drying, make the strips to hold the glass and the picture in place on the back, and glue them. A few fine brads may be driven from the back to add strength, but do not drive them until the glue holding the blocks is absolutely dry. Then glue on the back piece gered of wood, however, should be avoided. Select a good cigar box, take it apart carefully, scrape off the paper and clean with sandpaper held on a small block. Lay out the frame proper. The glass and picture space is left open at the top so that the picture may be changed at any time. The frame may be made either to hang on the wall or to stand (or whatever part is to be made) and use a knife to cut the outline deep into the wood. Cut a hole in the waste material to allow a coping- saw blade to be inserted; then cut out the center rectangle. If a coping-saw is not at hand, cut deeply with the knife from both sides until the wood is removed. Make the cuts on the outside edges with saw and knife, or with the knife alone. Smooth up the inside and outside edges with a wood file or sandpaper. Make the square and rectangular blocks used to build up the surface as indicated. The edges and ends can be sandpapered best by laying the sandpaper down and mov- ing the block overit. Lay out the spaces for the notches on the edges of the blocks 3/16 in. apart as nearly as possible. The Sawing out the picture opening Notching blocks (at left), gluing them in place (above), and planing a thin strip (at right) on a table or a dresser. Apply a coat of mahogany stain and one or two coats of thin shellac or varnish. In making the candlestick, the upright piece is composed of four thin pieces of wood, joined boxlike to form a post 1 in. square at the top and 34 in. at the bottom. An auger bit can be used in mak- ing the hole for the candle, but the coping-saw or even the knife alone will do the work. If an auger bit is used, cut out some wood for the ‘‘spur’”’ of the bit or it will crack the _ board. It is also well to make the hole on a larger piece and afterward trim the ». piece to the re- Gus quired size. A =eaees i piece of green felt Hxeo ow under the candle- stick finishes it off.—E. E. Details of a notched candlestick —— © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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we even, thin, ile or 1 on * the t the uient, Building Model Motor-Trucks (Continued from page 94) s by 4 by 40 in. strip brass for upper frame 4 4/16 by 4 by 80 in. strip brass for lower frame fastening : Gf andite by % by 18 in. brass for swing strips and il by % by 8 in. brass for axle boxes +} vy % by 8 in. angle brass for spring plates 1/16 by % by 12 in. strip brass for journal-box lids , by 12 in. thin spring brass for contact shoes ; Open spiral spring 3/16 in. in diameter, 12 in. r hody springs ; , gio 3/32 by 14 in. machine screws with tap and i suit F Ke ont. ¥ by 1 in. machine screws with tap and i uit anil ae 34-in. round-headed wood screws for end- fastenings, etc. : bean, flat-headed wood screws for attaching r bolsters, etc. ; uP Phese.lengths and amounts are in excess of actual requirements to allow for unavoidable waste and spare stock In the way of tools you will need: An assortment of twist drills containing at least every alternate size from No. 10 to No. 60 A drill gage from 0 to 60 a A breast or electric drill stock to hold up to 4-in. in. fine 8-in. hacksaw blades with frame 1 doz. fine scrollsaw blades with frame A few flat, three-cornered and rat-tail files ; An assortment of square- and round-nosed pliers with wire cutters . Medium-size tin snips A small anvil ; : A vise with jaws at least 2 14 in. wide Ordinary household tools, such aslight and heavy hammers, saws, and the like, are taken for granted. If possible, provide yourself with a pair of calipers, a set of small taps and dies, with tap wrench and die stock, in sizesfrom %in.up. The \-in. size will be handy when you come to making controller handles and similar work. You may also require 16 % by 1 in. bolts such as can be had from any dealer in model-making supplies, but these will be mentioned later on. Make sure that all your brass stock is square, flat, and free from warp - us begin with the axle boxes. Study Fig. 6 of the mechanical drawings on page 94—the top and side views of the journal box stock after it has been drilled. The 14-in. holes are for the jour- nals and the 1%-in. holes are for the bolts that hold the journal boxes. Before being cut apart, the strip of boxes forms an excellent templet for bor- ing the box bolt holes in the upper and lower side pieces. Remembering that the wheel base of the truck is 334 in., note that the journal holes A and B are also 334 in. apart. From this it follows that the bolt holes 2 and 3 and 7 and 8 must correspond with the bolt holes in both upper and lower side frames. For the side frames, cut 8 pieces 7 in. long; 4 of these are 1{ in. and 4 are 1/16 in. thick The lower frame is only 1/16 in. thick, while the upper is 1% in. thick. Take one of these pieces and scratch a mark across it precisely in the center. Now place it in the vise with the still assembled boxes so that the 14-in. faces of each piece are accurate contact through their entire length and bolt hole No. 5 exactly bisects the scratches in the center of the 14 by 14 in. frame piece. Now: using a )-in. drill and bolt holes 2 and 3 and 7 and 8 as guides, drill through the side frame. Remove the journal box piece and putting the frame piece alone in the vise, drill a 1%-in. hole ¥ in. each side of the center scratch, and another 1{-in. hole with its center 3/16 in. from each end of the frame piece. If you have been careful to see that all holes have been drilled accurately along the (Continued on page 102) - saving kinks. POPULAR SCIENCE MONTHLY SAVE HALF-INSTALL YOUR OWN PLUMBING 4x> HEATING BY OUR New ZLasy Method CAG ANY HANDY MAN ¢2n install his own Plumbing and Heating by our New Kasy Method and Save Half. In the past 50 years, we have saved our customers bun- dreds of thousands of dollars in the cost of: Plumbing Goods, Pipetess and Warm Air Furnaces, Stcam Boilers, HotWater Boilers, Water Supply Systems, Water Heaters, Bathroom Outfits, Pipes, Radiators, Valves, Supplies, etc. BIG “ax BOOK Tells the whole story. Shows the Hardin-Lavin New Easy Method. Send coupon with 25c (regular price 50c, refunded on first order) for your copy today. This Big, Instructive, Well-Bound ‘Handy Man” Book- Catalog shows 10,000 items in latest style, highest quality a Heating Fixtures and supplies at Whole- sale Prices. Hundreds of Trade Secrets Al:o shows many valuable diagrams, plans and elevations of simple installing systems, trade seercts and money, time and labor Most valuable book of its kind pub- Bonded Guaranty A 7) Or We guarantce that every eee ee eae article we sell from the € i smallest fitting to a com- TODAY. plete installation is perfect and exactly as shown and Read Our of the HIGHEST GRADE Guarantee that is possible to manufac- ture. We further guarantee ae A ‘ that if you are dissatisfied Write this magazine for any reason, you can re- or your bank about ]j turn any goods bought from our 50 years’ record ——s we will oe . refund your money plus of square dealing and freight charges you have about our new million paid. (Signed) dollar plants. OR- HARDIN-LAVIN CO. DER TODAY AND | Could Anything Be SAVE. ¥ OU CAN- Faircr? NOT LOSE. Super Improved Automatic Electric Water Supply System Absolutely reliable, fool-proof and simple. Can be depended upon to give lasting service with ractically no attention. No better outfit made or SHALLOW WELLS OR_ CISTERNS ET Complete WHERE WATER IS NOT OVER 22 FEE BELOW SURFACE. Mebesien a Runs in Oil $ggsoc Noiseless, double acting, brass fitted throughout and fully enclosed and ( ; “il moving parts run in oil ath which insures long life. Latest type oversize 1-6 Horse Power electric motor, operates economically and is thoroughly reliable; surplus lubricated by the ‘‘New Splash System.” All power to drive pump under all conditions, Outfits Complete— No Extras Complete Bathroom Outfit, built along practical and attractive lines. Highest grade possible to make. Shows that First Quality Hardin-Lavin products can be had at low cost. WHITE ENAMELED BATH TUB Cast Iron, heavy white porcel:.in, enameled inside and over the 3% inch turned-over rolled rim; outside painted, Newest Design. Fitted complete with heavy brass, nickel-plated compression bath faucet, withchinain- dexed handles, nickel-plated heavy brass adjustable waste and overflow and supply pipes to floor; width eas 30% -* peas Be 6 a 1t., weight 300 Ibs. cago A-50— Bathtub compl!cte as shown with iron-pipe connections. Special $3 I. 10 motor. System consists of pump with auto- matic air valve, oversize 1-6 Horse Power repulsion induction motor automatic switch set at 40 lbs., relict valve, shut-off valves, necessary pipe and fittinss asshown; one galvanized heavy pneumatic tank wit) pressure gauge, one % in. galvanized foot valve and strainer. Pump has % in. suction an i discharge. Outfit equipped with 60 cycle, 110-220 volt, single-phase alternating current If you have other current, state voltage, etc. No. A.—500. Water Supply System with 42 Gal'on Tank. Shipping Weight 300 Ibs. Price, com- Dlete, Special No. A.—501. Water Su ply System with 80 $98.50 alion Tank. Shipping Weight 340 Ibs. Price, complete, Speci: al’ $110.50 * No. A—502. Water Sup- stem with 100 ply Sy: Gallon Tank. Shipping Weight 380 Ibs. Price complete, Special $122.50 approval of the INSTITUTE OF STANDARDS. White Closet Outfit Improved, snow-white composition Chino Closet tank (beautiful and ine destructible); fitted with solid brass elevated noise less eo = improve china flushing handle. Medicine ::) Highest grade | Cabinet, Special....... Hi white vitreous ighest Grade White Enamel Steel; all joints electrically welded be- fore enamel ith four coats of baked enamel, inside and out. Has plate glass bevelled mirror, two plate glass shelves, heavy glass knob and enameled non-sag hinges. Cabinet is guaranteed to be entirely satisfactory and carefully crated to reach you in first class condition. Hang on any wall with two screws, Height 21 in., width 16in., depth 5in., wt. 35 lbs. weight 125 lbs. No: 5137—White enameled Cabinet, Special, reduced to.......-. $8.95 Highly polished, reinforced birch mahogany seat, with heav brass, nickel- plated bar hinges, flushing ell, supply pipe, Outét, complete as shown with iron-pipe cone nections. Special $19.95 Deev Apron Lavatory Late desizn, white porcelain enameled, cast-iron drop apron lavatory, sup- ported on concealed wall hangers; new low design, china indexed come pression faucets, heavy brass, nickel- plated adjustable supply pipes and trap to floor or wall, size 17x19}4 in., weight 120 Ibs. Chicago A-51—Lavatory. Com- ete as shown with lron-Pipe con- nections. Special, Pa Cieoemaed $11.75 Chicago A-53—Bathroom outfit, complete as shown and de- 2 All shipped from Chicago plant same day as order is received, Order today. You cannot lose. Heating Plants Cut-To-Fit Hot Water—Steam— Hot Air—Pipeless Hardin-Lavin_Cut - To - Fit Hot Water Heating Plants give highest heat efficiency at lowest cost. Boiler embodies best engineering; easy dump- ing grates; long indirect fire travel that insures complete combus- tion and greatest heat. Our modern equipment and 50 years’ practical ex- rience qualifies us to produce this oiler that will burn any kind of fuel, cleanly, pletely, an ically. WE HELP YOU PLAN. Every Hardin-Lavin Heating System is ficured to eliminate long runs of piping, to save valuable time, and expensive labor, ith our complete instructions and simple installing features, you can do the work yourself and save. We loan the tools if necessary. WRITE TO- DAY _ FOR Low WHOLESALE Free Estimate Send us roucth sketch, plan or blue print of your home and we will igure the wholesale cost of a@ simplified cut-to-fit Heating or Plumbing System that ex- actly meets your needs. We will show you many wrinkics where you can make money savings that will surprise you. r Bonded Guarantee protects you. Behind this, stands our million dollar plants and record of 50 years. MAIL COUPON TODAY HARDIN-LAVIN CO. When in sarcoma = E pea new plant at 106-16 W. Pershing Rd.. Chicago HARDIN-LAVIN CO., 106-16 W. Pershing Rd., Chicago, III. Gentlemen: Enclosed please find 25c (%4 regular price) for which send me your Big Complete “Handy Man’ Book «Catalor with special lesale discount sheets and FREE Bulletin Service. I am interested in: Water Sply. System ( ) Plumb. Fixtures Steam Heat. Plant ( ) Bathroom Outfits H. W. Heat. Plant ( ) Pipeless Furnace Note:**Handy Man" Book is FREE if order accompanies coupon. NAME.. eee eeeecerecoeses eeereeee Cee e eee eeseessresseseeeeeee See page 25.

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nt cee eg Se Now Boice-Crane Junior Saw POPULAR SCIENCE MONTHLY At Your Service The courteous girl at the switchboard speaks the first word in more than two million conversations an hour. Presiding day and night at the busy intersections of speech, she is always at the call of the nation’s homes, farms and offices. Out of sight, and most of the time out of hearing of the subscribers, little is known of the switchboard girl—of her training and supervision under careful teachers, and of her swift and skilful work. Likewise, little is known of the engi- neering problems necessary to bring the terminals of fifteen million telephones within the reach of a girl’s arm, or of the ceaseless work of maintenance which in fair weather and storm keeps the mechanism fit and the wires open. America’s millions of people must have at their command means of direct and instant communication, and the Bell System must ever be in tune with the demands of national service. These are the components of America’s system of teleph- ony: The best of engineering, of manufacture, of facilities— and a personnel trained and eager to serve. AMERICAN TELEPHONE AND TELEGRAPH GOMPANY AND ASSOCIATED COMPANIES BELL SYSTEM One Policy, One System, Universal Service $25.00 in PRIZE Let Boice Help You Build It! See top of page 8 in front of book for details. No matter what you want to build. Boice can help you. e’ll send you the Buy Or any other Boice-Crane machine on monthly payments. He gives you surpass: prices and values an with a positive money-back guar- antee. Mac’ is i: spine ghown will saw, Pay a few sand, grind, miter, . tenon, ete. Sturdy, accurate, cents a day economical. Ww: % sock, . old with of without motor. the Boice way! ice W.B.&J.E. BOICE Dept. P. S. 4-A, Toledo, Ohio ** World's Largest Makers of Smatt ‘Bench Machines” fully the center lines of the bolt holes, Building (Continued from page 101) . center line, the frame piece may be used as a templet for the remaining frame pieces. Unless you have access to a drill] press, it is advisable to have the dril] of at least the journal box stock done machine-shop. You now can cut apart the journaj boxes with a fine hacksaw. Follow care. ing ata Either 14 by 1 in. machine screws o; bolts may be used for securing the journal boxes to the frame. If screws are used the holes in the lower frame piece must be slightly less than 1% in. so that they can be tapped. This method necessitates drilling the 4 upper and 4 lower frame pieces separately, .but is cheaper and avoids the possibility of losing any nuts, The bolt method is shown at the right of Fig. 1, and the machine-screw method at the left. A refinement in the journal boxes, which ' may be introduced if desired, is illus. trated in Fig. 2. A -in. hole is drilled from the center of the bottom of the box until it intersects the bottom of the jour- nal hole. This is for holding a bit of cotton waste for lubrication. If you drill this hole, remove the burr by filing a de. pression not more than 1/32 in. deep in the bottom of the journal hole. voy now may attach the journal-box lids. Just above the top of each journal hole, drill a hole a trifle smaller than your 3/32-in. machine screws and tap this. Then cut the box lids from 1/16 by % in, strip brass, as in Figs. 1 and 2. Round of the top of the lids and drill a hole for the screw large enough to admit the screw clear to its head, so that the lid can be screwed down tightly enough to act as an end stop for the journal. When your four side frames and boxes are assembled, you are ready to add the wooden end beams and transoms. Trim three strips of fairly hard, straight- grained wood, each about 18 in. long, to the cross sections shown. See that the edges are truly at right angles and all sur- faces smooth and free from warp. There must be no knots. Cut four pieces from this stock % by % by 41% in. long for the end beams and round the ends, as in Figs. 1 and 2. Take two of the assembled brass frames and with the box lids screwed flush with the boxes, slip them over the journals. Hold them together temporarily with two rub- ber bands. Then insert the end beams, making sure their @nds project equally at the corners. Mark the locations of the corner screw holes on the upper side, re moving the end beams, and drill for 3¢-in. round-headed wood screws. Insert the screws, turn the truck upside down, mark and drill for the under side, and square the whole frame. ; It is vitally important to maintain squareness throughout your work. Em ploy a small try-square constantly. The two trucks at this stage should run 4 smoothly as a billiard ball. The next article will take up the wooden bolsters and the mounting of the motor gearing, and springs. © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. ay PF

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ep in al-box ournal n your » this. 3% in, ind off for the screw can be t as an | boxes dd the Trim raight- ong, to iat the all sur- There 6 by ¥4 ms and ». Take 1es and rith the . Hold wo rub- beams, ually at ; of the side, Te or 34-in. sert the n, mark | square naintain k. Em- ly. The Tun ag ‘wooden > motor;

_ April, 1925 Mistakes in Painti Household Painting Guide POPULAR SCIENCE MONTHLY

SHERWIN - WILLIAMS HOUSEHOLD PAINTING GUIDE

‘TRADE MARK TO PAINT— |TOVARNISH—| TO STAIN— |TOENAMEL SURFACE USE PRODUCT USE PRODUCT USE PRODUCT USE PRODUCT NAMED BELOW NAMED BELOW NAMED BELOW NAMED BELOW AUTOMOBILES. ..... S-W Auto Enamel sa j WALLS, Interior Old Dutch? (Plaster or Wallboard) Enameloid WICKER............ Rexpar Varnish Floorlac Old Dutch Enamel WOODWORK SWP House Paint Sear-Not Varnish $-W Handcraft Stain | o1g Dutch Enamel INNGTIOE 0.005000 eee Flat-Tone Velvet Finish No. 1044 | 3)" Out Stain

Floorlac

‘Enameloid

For Removing Paint i For Cleaning Painted and Varnish use and Varnished Sur- Taxite— quick — easy bead faces use Flaxoap. A mpeg ome Made from linseed PAINTS AND VARNISHES —can be used by anyone—on any

SHERWIN - WILLIAMS Payment Plan Arrangements have now been perfected by Sherwin-Williams whereby the paint- ing of residential property may readily be arranged on a convenient payment basis. Recognized business practise is now, therefore, made available to the property owner without difficulty or red tape. The Sherwin-Williams “Paint Headquarters” Dealer will gladly give you full information.

oil—contains no free alkali—restores origi- nal lustre.

© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. ey Le ae

For Screens For Furniture How To Hire a Painter Give the job to a good painter when you hire a man to paint your house. “Paint Head- quarters”’ will recommend good men. Good painters are worth knowing. If you hire a painter, hire a good one. eee ce em te EIT SOS sc ch I ATCT

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AUGHAN Vanadium Hammers are aris- & BUSHNELL tocrats among hammers. Made from special formula vanadium steel —handled with the best grade hand- shaved second growth white hickory —designed with a special non-slip claw that grips either a brad or a spikew— and equipped with a Vaughan’s Expansion Wedge that firmly locks the handle tight—they are made for you craftsmen that buy quality tools. V & B Unbreakable Planes bear the same reputation as V & B Vanadium Hammers. They are drop forged— not cast—from a solid bar of V & B Supersteel, and stand the falls and accidents that would break an ordi- nary plane. They are furnished with all vanadium steel blades and walnut handles in the sizes you'll want. Your hardware dealer will heartily recommend these two tools. Ask to see them when next you are in! © Vi POPULAR SCIENCE MONTHLY

AAUGHAN & BUSHNELL MANUFACTURING COMPANY

CnAa. 2li4 Carroll Ave.~ rs of Fime Toots ~ Chicago, WL U.S.A. |

HE erection of aerial masts has often resulted in the marring of attractive lawns or homes with unsightly, makeshift poles. Those radio fans who have attempted to erect neat pipe masts frequently have given up in disgust and discarded the bent, twisted, and unmanageable _ re- mains of their un- successful efforts. It is almost impossible to erect a 50-ft. mast after the pipes have been assem- bled, as it will bend, vibrate, and twist. The most prac- ticable method is to telescope three lengths of different sized pipe. The smallest or upper section should not be less than 34-in. pipe size. Set up the telescoped pipes in a hole 4 or 5 ft. deep. Fill in with concrete or well tamped earth and use three guy wires to brace the largest or lowest section. Two men, working from ladders placed on opposite sides of the erected pipe, then raise the top or smallest section until it has been lifted three-quarters of its length out of the middle section. A bolt is slipped through a hole previously drilled

How to Erect an Aerial Pipe Mast By B. Francis Dashiell

Raising the upper pipes

for that purpose, go ag to prevent this section from telescoping or sliding down within the next larger size. The middle or second section (now supporting the top or smallest section) then is raised and a bolt used in a similar manner to prevent its telescoping within the largest or lowest section. Guy wires, which were previously at- tached to the top of the second section, Pas are fastened to the #2. same anchor posts oe used for the guys of the lowest section. It is not nec to attach guys to the top section, but itis well to use a single wire to counteract the pull of the aerial wires. By using this method a 50-ft. mast may be raised in less than one hour. It is im- portant, however, to select pipes that slide or telescope easily. Three 20-ft. lengths will make a mast that will be from 45 to 50 ft. high. Because of the weight of the pipe, it is not advisable to use more than three pieces. One advan- tage of this method is that the pipes can be painted before erection, and lowered when necessary for repainting.

Old Can Forms Ash Receiver HE ash receiver illustrated costs nothing to make, has a large capacity, and will not readily spill. It is made from a can that contained toasted almonds. Pictures are pasted over the reading matter, while the rest of the surface, decorated with panels of purple and yellow, remains unchanged. A little shelf upon which a_ lighted cigarette may be laid, is formed from

An ash receiver of large capacity the lid. This is cut across one-third the distance from the end. One end of it is | bent to form a hinge joint around a piece of stout wire or a nail, which is soldered in place as shown.—EDWARD H. FLAHARTY.

Butterfly Paperweight Is Attractive Desk Ornament

By Clyde E. Volkers ‘id YOU have stored away somewhere a discarded glass paperweight, you can convert it into an attractive desk orna- ment by replacing the colored print with 2 small butterfly or moth. The glass first is cleaned thoroughly. Cut a piece of stiff paper or thin card- board that will fit the bottom of the paperweight. In the hollow cavity of the glass, place the butterfly so the more attfactive side will be seen from the top. Arrange a piece of brightly colored grass, or a dainty bit of flower over the butterfly. ‘As a background use a thin sheet of white or stained cotton or the silky down from milkweed pods. Glue the card- board to the £& back of the weight to hold the cotton, flower, and but- terfly in place. Acetic glue is excellent for this purpose. It is made by heating 18 parts of glue flakes (previously softened by soaking overnight in a little cold water) with 2 parts of acetic acid until a thick liquid is formed.

< * at : ay ce Le A unique paper weight

— nh

1S} This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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ction thin ‘tion) s bolt anner oping st or which ly at. top of ction, (0 the uys of ction. it it is ct the it may is im- 3. that 20-ft. vill be of the ible to advan- yes can ywered ent rhere a ou can : orna- it with yughly. 1 card- of the of the > more he top. 1 grass, tterfly. f white m from ned by | water) a thick = SEE ERLA - RECEIVERS Inherent Erla advan- tages in power, tone and selectivity are now available in beauteous complete Erla receiv- ers. Retail prices range from $67.50 to $225. Both price and per- formance place Erla re- ceivers among the sen- sations of radiohistory. POPULAR SCIENCE MONTHLY More Power per Tube brings Greater Radio Most Economically Triple power is the basis of Erla Supereflex records. Tubes, as used in Supereflex, simultaneously amplify received radio frequency currents, reflexed radio and reflexed audio frequency currents. So 1-tube Supereflex rivals the power of conventional 3-tube circuits. And 3-tube Supereflex readily outclasses the ordinary five! Only such power can give you the thrill of Supereflex distance and volume; always with Erla crystal-pure tone—and with uncanny selectivity that gets what you want when you want it. This finer radio is brought within the reach of all by Erla Supereflex CIR-KIT, the factory-sealed carton of genuine Erla apparatus for building Supereflex your- self. Anyone can follow the CIR-KIT assembly plan perfectly, using only screwdriver and pliers, without drilling or soldering. Pride of workmanship, extreme economy, priceless radio performance, are yours in Erla Supereflex CIR-KIT. Select your model at the Erla store. 1 to 5 tubes, an- tenna and loop types.’ Electrical Research Laboratories Department S, 2500 Cottage Grove Avenue, Chicago ERLA © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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POPULAR SCIENCE MONTHLY April, 1995 The Fine Finish of BROWN & SHARPE TOOLS Is Part of Their Quality— An Indication of Excellence Hizh accuracy, together with superiority in every point of tool design, are basic qualities in Brown & Sharpe Tools. Fine finish is one of these qualities. Just examine closely any Brown & Sharpe Tool. Its fine finish is an indi- cation of its excellence— an excellence which can be had only in Brown & Sharpe Tools. Have you seen the new Brown €F Sharpe Small Tool Catalog No. 29? Let us send you a copy. Brown & Sharpe Mfg. Co. Providence, R.I., U.S. A. © Dee & SHAREE ‘“‘Standard of the Mechanical World’’ OOLS Pee: The Home Workshop Few Tools Needed to Builg Sturdy Wooden Plant Stands ‘T HERE is a Robinson Crusoe streak in all of us. If the first trial of a joint in either woodworking or metal- working proves an error, what of it? The second or third will be right. Even the would-be mechanie who has never made as much as a box, will learn how true this is if he will try his hand at making a pair of pedestals or stands by either of the methods shown in the accom- panying draw- ings. The tools needed are a saw, a plane, a hammer, a cop- ing or compass saw, brace and bits, a square, and a nail-set. You can get the wood planed to size at the mill. All Details of the first pair are shown at the left; of the second pair, at the right you need to do is to saw off the pieces to the length shown, square the ends, and put them together. No mortises or tenons or dow- eled joints are used. Allowing for some waste, the material needed for the first pair of pedestals il- lustrated is as follows: The second pair 2 pes. 114 in. square, 9 ft. long 1 pe. 1% in. thick, 7 in. wide, 3 ft. long 8 large rubber-headed tacks ¥ lb. tenpenny finishing nails 2 sheets No. 0 sandpaper Saw the 9-ft. pieces into eight 24in. lengths, seeing that the ends are square. Cut the 3-ft. piece to make four 7-in. squares, which will form the tops and bottoms. Draw diagonal lines across the (Continued on page 109) —— 1S} This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. radi end suff und radi cori that accl insi drix are The wa) var: pail

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of a etal. The earn 3-14- 24-in. uare. 7-in. and ss the Bottom view of one of: the trucks’ and how it is used simply Made ‘‘Skates’’ Aid in Handling Heavy Radiators ER my father strained his back ponell a radiator, I devised the two small trucks or “skates” illustrated. Each one is made by screwing four casters on a wooden block, 2 by 4 by 12 in. One pair of casters is set back from the end about 9 in.; the other is even with the end. In use, the overhanging end of the skate is placed under the end of the radiator. By pressing down on the other end of the skate, the radiator is lifted sufficiently to allow the skate to slip under. With a skate under each end, the radiator can be wheeled easily.—R. B. Sturdy Wooden Plant Stands (Continued from page 108) corners of both sides of these pieces so that the legs and nails may be placed accurately. The uprights are kept 114 in. inside the edges. Two tenpenny nails are driven into each joint. The rubber tacks are driven into the base near the corners. The completed pieces are stained and waxed or stained and given a coat of flat varnish. The material required for the second pair of pedestals is as follows: 2 boards 1 by 534 in. by 14 ft. 1 board 1 by 11 in. by 4 ft. 1 strip 1 by 1% by 16 in. A few sixpenny and tenpenny nails The 14-ft. boards are cut into eight lengths of 3714 in. The ornamental holes are marked in the center of each piece, beginning 14 in. from the bottom and Tunning to 1114 in. from the top. After boring the holes, cut out the 14-in. strip with a compass saw. _ The four top and bottom pieces are 11 In. square. They are fastened to the sides 1 in. from the edges with four ten- penny nails at each joint. The eight feet are sawed from the 1 by 11 in. strip and fastened at the corners of the bottom with two sixpenny nails in each joint. Sandpaper the pieces before assembling, making the strokes lengthwise with the grain. The wood for the tops and bottoms should be planed before being sand- Papered. After assembling, the edges are chamfered or rounded off. The heads of the nails are set ! 7 POPULAR SCIENCE MONTHLY CREAM 4 in, deep and the indentations filled with putty that is colored with stain.—J. T. GARVER, My Life Work The finest shaving cream you will ever know Let me send you a tube to try By the Chief Chemist GENTLEMEN: In less than 4 years, Palmolive Shaving Cream has gained top place. Its success is a business sensation. Will you do us the courtesy of trying it? Men literally are flock- ing to it. We asked 1,000 men Our first step was to ask 1,000 men what they most desired in a Shaving Cream. All of them agreed on four things. But one requirement, and the greatest of all, is something no man mentioned. That is, strong bubbles which support the hairs for cutting. We made 130 trials or tests We made up 130 formulas which we discarded. Then we attained, by many times over, the best Shaving Cream in existence. Today Palm- olive Shaving Cream is winning men by the millions, as they try it. Don’t change from the cream you like now until you see what Palmolive Shaving Cream does. But make this test. Try ten shaves, and let the results show if we have excelled the rest. 1—Multiplies itself in lather 250 times. 2—Softens the beard in one minute. New 3—Maintains its creamy | fullness 10 minutes Delights on the face. 4—Strong bubbles hold the hairs erect for cutting. 5—Fine after-effects, due to palm and olive oil content. To add the final touch to shaving luxury, we have created Palmolive After Shaving Talc —especially for men. Doesn’t show. Leaves the skin smooth and fresh. Try the sample we are sending free with the tube of shaving cream. Clip coupon now. THE PALMOLIVE COMPANY (Del. Corp.), Chicago, II. PALMOLIVE SHAVING and a can of Palmolive After Shaving Talc Simply insert your name and address and mail to Dept. B 969. Address for residents of Wisconsin, The Palmolive Company (Wis. Corp.), Milwaukee, Wis. Address for_residents other than Wisconsin, The Palmolive Company (Del. Corp.), 3702 Iron St., Chicago, Ill. . © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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| A Keener Edge--- For jungle. undergrowth, sugar-cane ---perhaps even tropic politics---cutting tools must be razor sharp and shaped just so. It’s the file that keeps them properly edged, adding impetus to even primitive industry. From the gold mines of Alaska to rubber plantations on the Amazon---whetever tools need sharpening and files must render con- stant and faithful service--- NICHOLSON FILES are preferred. In your home, too, you can quickly sharpen every cutting edge with a NICHOLSON FILE---one of the many reasons why they belong in your tool equipment. NICHOLSON FILE CO. U.S.A. Providence, R. |., NICHOLSON FILES ~~ a File for Every Purpose he Home Workshop SSS Fumeless Chicken Brooder Costs Little to Construct By L. B. Robbins \ , JHILE there are many t brooders for raising chicks, the en illustrated has been tried out with th greatest success for several seasons by tne builder. It can be built for practically nothing and will raise easily from 50 to 60 chickens until they are six weeks old. It is used indoors. Poisonous fumes from the lamp—the most dreaded thing to contend with jp brooding—practically are eliminated, yet Brooder with hover removed te the heat is distributed so that the chicks can secure any degree of warmth. The body of the brooder consists of a wooden frame 32 in. square by 12 in, wide. Across the top of this frame tack a piece of sheet zine or iron and turn the edges down all around. A strip of sheet asbestos between the edges of the board and the metal will make a tight joint. This completes a strong, boxlike structure with an open bottom and a metal top. Nail four pieces of 3-in. furring around the box and over the metal. Use long wire nails to go through the furring and © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. the metal and into the frame. Then | floor this second structure over with thin, | matched (tongued-and-grooved) boards, | making as tight joints as possible. This | construction forms a 3-in. air space above | the lower frame. Cut a 6-in. hole in the center of the | flooring and invert an old cooking dish SHEET IRON CORRUGATED BOARD FENCE. HOVER-ON 6" en i WOODEN LEGS [ii] SLIT FELT PERFORATED DISH em N s DOO PLATFORM AND » LAMP RUNWAY Heat from the lamp is transmitted through a metal diaphragm to a hot-air radiator over it, fastening it to the floor with small brads. The dish should be punched full of small holes to radiate the warmth from the hot-air chamber. A square hole is sawed in one side of the body of the brooder, as indicated, and fitted with a sliding door. The hover consists of a thin wooden panel 24 in. square set on four wooden legs 6 in. high. Fit some sort of a handle (Continued on page 111) sor for stal bla eas bla sph car last the the INS old tor not of felt als —

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8 of One tk. y tne to 60 a —the th in 1» yet chicks Ss of a 12 in. tack a n the sheet board joint. ucture top. round e long ig and Then h thin, yoards, This above of the g dish rough diator th small hed full th from side of ted, and wooden wooden 1 handle Sealing-Wax A Toys and Models EALING-WAX is a useful medium for making interesting little toys as well as colorful models such as the one illus- trated, which is an amateur theatrical scene, built on the scale of 14 in. to 1 ft. The back drop is a piece of illustration poard painted with water colors. The wall and gate are stiff drawing paper. The snow on the wall is white wax. By drawing the soft wax slowly off the edge and then cutting the threads with a scis- Miniature scene for amateur theatricals made with sealing-wax on illustration board and paper sors, realistic drifts and icicles are formed. The lamppost is a 20-penny nail standing on its head and covered with black and white wax. When the wax is soft it can be molded easily with the fingers or with small knife blades and large needles. Cylinders or spheres are formed by twirling the wax carefully over an alcohol flame. As the last step, a brilliant gloss can be given to the work by running it quickly through the flame.—KENNETH M. SWEZEY. InsoLES for shoes may be cut from an old felt hat. They are fully as satisfac- tory as commercial insoles and cost nothing. If thoroughly washed, a piece of old felt hat makes a good rubbing felt for finishing woodwork. The felt also is useful for cutting gaskets.—W. L. Fumeless Chicken Brooder (Continued from page 110) to the center of the top and tack a 6-in. strip of felt around the edges. Slit up the felt at intervals of 2 in., so that the chicks may pass in and out of the hover. For heating use a regulation brooder lamp or a common lamp with short chim- ney. Light it and place it under in the center of the lowest compartment. Pro- vide a few holes along the top edge of the wide frane, below the metal ceiling, to carry off the fumes. The air in the 3-in. space above then becomes heated without odor. The heat passes out of the holes in the heating drum and warms the interior of the hover. An average size flame will Maintain 90 degrees in cold weather. Corrugated board, tacked about the brooder as indicated, can be used to fence the young chicxs in for the first few days and then extended as they increase in age and size. An extension platform can be hinged to the front to furnish the birds More floor space and finally let down to orm an inclined runway when they are allowed to have an outside run. This brooder may be cleaned readily, is $$ Safe, and will raise strong, healthy chicks. eee POPULAR SCIENCE MONTHLY WORTH WHILE TOOLS HERE is satisfaction in the ability to tackle odd repair jobs about the home; and if one has the energy and determination to do some of this work himself, the savings in time and money will be considerable. The kind of tools used often determines the quality of the work. To be sure of the best results, get the right tool for the purpose. There’s a large variety of Pexto Tools made in all practical styles and sizes. You can’t go wrong if you insist on these century-famous tools. For the mechanic and for gen- trated above, will give a life- : time of dependable service and rey stand up under the severest ‘roughing.’ Its ball-bearing chuck gives the Pexto Brace a grip that THE PECK, STOW & WILCOX CO. SOUTHINGTON, CONN., U.S. A. IS) This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 268. All Pexto Tools are backed by a cen- eral home use, the. Pexto Sam- tury of tool making experience. The son Ratchet Bit Brace, illus- ine consists of Bit Braces, Hammers, Screw Drivers, Hatchets, Snips, Squares, Wrenches, Pliers, Prun- ing Shears, and many other small tools. It is easy to procure Pexto never lets go. It will hold round, 1 ols as they are carried by practically square or taper-shankdrills. The all progressive dealers. Booklets cov- Samson is the kind for you—it’s ering our lines are available for free a boon to the “home mechanic.” _ distribution. Wy Ask for them.

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‘you never had a chance! “Four years ago you and I worked at the same bench, I realizcd that to get ahead I needed special training, and decided to let the International Correspondence Schools help me. I wanted you to do the same, but you said, ‘Aw, forget it!’ You had the same chance I had, but you turned it down. No, Jim, you can’t expect more money until you’ve trained yourself to handle bigger work,” There are lots of “Jims” in the world— in stores, factories, offices, everywhere. Are you one of them? Wake up! Every time you see an I. C. S. coupon your chance is staring you in the face. Don’t turn it down, Right now over 180,000 men and women are preparing themselves for bigger jobs and better pay through I. C. S. courses. You can join them and get in line for promotion. Mark and mail this coupon, and find out how. ee 2 ea See NE RRR SN ee ee SMR ER INTERNATIONAL CORRESPONDENCE SCHOOLS Box 7644-D, Scranton, Penna. Without cost or obligation on my part, please tell me how I can qualify for the —— or in the subject before which I have marked an X BUSINESS TRAINING COURSES Business Management Salesmanship Industrial Management Advertising Personnel Organization Better Letters Traffic a Show Card Lettering Business CJ Stenography and |Banking and } Banking Law 0 Business English Accountancy (inc Seding C.P.A.) () Civil Service eee Cost Accounting Railway Mail Clerk OOD Cemmon School Subjects Private Secreta High School Subjects \Spanish a French Dlustrating TECHNICAL AND wer _ Electrical Engineering Arch’ Electric Lighting a Architects’ Blue Prints \Mechanical Engineer Contractor and Builder }Mechanica!l Draftsman |Machine ee Practice Concrete Builder ns Structural Engineer Automobile Work Airplane Engines Agriculture and Poultry Mathematics ing Steam Engineering Li Badio 3-6-24 City State. (] Architectural Draftsman Chemistry (J Pharmacy Occupati on. Persons residing in Canada should send this coupon to the International Corr Canadian, ‘Montreal. Canada Not Makes100 Al WEEK ¢ ? New lay! wearing is bea ailored FREE RAINPROOF week Hand Cap? Just think—S. W. Allen of Cal:- fornia made $40.80 in one day’s joyful $10 a Day in Spare Time Hundreds of men arer profits of $10 a day in just their spare time. This cap is so superior to store caps every man wants one. E Taylor “Cap is RAIN- PROOF—the moisture can’t Bo in. Choice finest wooiens and latest styles. No experien . Get acap for ouepelt FREE. Write at once for our FREE Selling YLOR CAP MANU FACTURERS, Dept. 9.p, "Simclanate Obie L imited. INSIDE OF ROOM POPULAR SCIENCE MONTHLY ew to Cut a iiiaaew nonaion in a Frame House O CUT a new window opening in a frame house presents no great ob- stacle to the skilful home worker. The location for the window in the room is fixed by the individual circum- stances in each case. seen, however, if in that position it would injure the appearance of the residence from the outside. This may be judged by measuring from the outside corner of the house, allowing about 6 in. more than the distance across the room or rooms as measured inside. It remains to be Should there be a window above or below that comes almost:in line with the place for the opening, keep the new win- dow exactly in line, if possible, even if the location is not so desirable on the inside. If the window is smaller in height than others on that side of the house, it is usu- ! ~~ w OPENING TO BE ; =FINISHED LEVEL AT TOP WITH OTHER WINDOW F OPENING READY TO SET THE FRAME VT Inside and outside view of opening cut and ready for placing a new window frame ally best to make the new window line up at the top with the others, as illustrated. This brings the window higher from the floor from the inside, but this is not un- usual and often no disadvantage. Before cutting the opening, tap the plastered wall to find the location of the studs or vertical members of the house frame. inch or so, the cutting out of one side stud If by changing the position an ean be avoided, do this; it saves much time. For double-hung sash, that is, the ordinary sliding sash with weights, mark the proposed opening on the wall 614 in. wider and 5 in. higher than the sash size. For example, if the pair of sash are 2 ft. 6 in. by 5 ft., the opening should be 3 ft. ¥ in. by 5 ft. 5 in. If casement sash shat weights is used, the allowance in width need be only 214 in. more than the sash. Cut out the plaster on the lines with a chisel, breaking out a strip about an inch wide to expose the lath. Then cut through the lath with a coarse compass (Continued on page 113) Tried by a thousand trails (CARLETON CANOES are built to staud the gaff of years of the hardest service. They do it too. Ip over a quarter of a century of manu- facture we have never had one dis satisfied user. Carleton Canoes are wonderfully light. They are beautifully balanced, fast and surprisingly easy to handle. And Carleton Canoes are unusually reasonable in price. Send for our new illustrated catalog, It gives prices and complete informa- tion. Write for your free copy today, Tue Car.eton Canor Co., + re: Street, Old Town, Maine, U Cro ON © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. ————— Protect Your Tools with - NWOT, Your valuable tools can be protected absolutely from rust. Cover all your tools that you aren’t using regularly with a thin coat of NYOIL. Keep a can in your tool bona The patented cap prevents it from leaking. emember—Summer e worst season for rust. NYOIL i is a highly refined oil that does not color or stain or gum. Makes an excellent polish for pianos, automobile and other highly finished surfaces. Buy Nyoil of your dealer or write us. W. F. NYE, New Bedford, Mass. se gps °° FREE ‘s “ith 3 ft. Telescope _— pie and Fobiacts ae away just ee rates were close; see M mand, Stars as never before. Opens. over 3 ft. long, 5 sections, brass bound, owerful mses. Useful Gr ait at get aes away Mrs. Horn. **Read numbers C, . Palmer Thou sands rite today; on arrival of 8 ft Ryeader ith FREE Case 2 7 - Zz Postman only $1.85 plus @ P oenn ies postage, Satisfaction Guaranteed. FERRY & CO), 3224 N. Halsted St.. Dept. 9784, CHICAGO toyou Free for 30 days trial on you Fi Your Wa choice of 44 Styles, colors and sizes of the famous Ranger er Express pre- (fy paid. Bicycles $ 1.60 and Up. _ “a i : 5 a Mon eirle easily make the bir sycie earn the de rt mg meen paymi ; nts. t at d equi men ives wahecls lamps fond eau foment ot NG able tactory CYCLE and marvelous ee w RADIO SETS—AUTO BODIES SEND FOR THE ennai agg CATALOG : pe Our on Loy International Bedy Werks, 914 W. Obi St., Da ch ‘Chicag, Ik $25.00 in Prizes See top of page 8 in front of book for full details See page 25.

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1s olutely a ing regularly ur tool chest, ber—Summer is Prices. | b money by at. 8, Chicas, I ——— “1ZeS or full details Pads Protect Your Hands when Lifting Rough Objects OR rough, heavy lifting, nothing pro- F tects the hands better than the pads illustrated. They are made by cutting from an old in- ner tube two oval pieces, about the size of dinner plates. In one end of each is cut a slit long enough to admit a hand. In use, the handsarethrust. through and the pads are pinched between thumbs and forefingers. Besides being inexpensive, they have the added virtue of not making the hands perspire as do gloves.—E. M. L. How to Cut a Window Opening (Continued from page 112) saw. Also cut out the 2 by 4 in. studs that have to be removed. You then are ready to work from the outside. Although at times this may be done from a ladder, it is a great advantage to rig up a scaffold opposite the opening to be cut. It usually will be best to order the window frame, sash, and inside trim com- plete. When doing this, request that the outside casing be sent loose. The casing then will come tacked lightly to the frame: Measure the frame with the casing on and mark the opening carefully on the beveled siding of the house with a straight- edge and plumb. In cutting the opening, the edge of the sheathing (B) should project about 2 in. beyond the edge of the siding (C) and a section of the siding (A) should be re- moved both at the top and bottom of the frame, to be replaced after the frame is setup. The drip cap on top of the frame should be covered with metal and painted before the upper piece of siding is put in place. At the bottom of the sill a groove will be found into which the bottom piece of the siding fits. Take care to nail the casing very solidly to the wall and frame. WHEN boring holes in wood without a depth gage, it is possible to have all the holes the same depth by counting the number of turns taken for the first hole and using the same number of turns for all the others.—M. E. S. © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. POPULAR SCIENCE MONTHLY 113 SIMONDS CIRCULAR SAWS HEN you specify SIMONDS in ordering a solid tooth circular saw¥or any other style of saw, you can be certain that its quality is protected not only by Simonds near- century of experience in making the finest cutting edges of tem- pered steel, but that constant laboratory tests and development work ‘assure you that your selection represents the very last word in cutting tool manufacture, 4 rod (Fi, ti.) T fag No matter what your cutting problem may be, put it up to ! #; Simonds, either through your supply house or dealer or direct. ¥/ ae * ' Wherever men _ depend upon : cutting tools } _ most SIMONDS SAW AND STEEL COMPANY © Fitchburg, Mass. The Saw Makers” Established 1832 Branch Stores and Service Shops in Principal Cities SIMMONDS Pronounced SI-MONDS SAWS FILES KNIVES STEEL

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114 If You Can Ham a Tune Send for this New Offer If you can hum a tune you can now learn to play a musical instrument quickly and easily. Think of the pleasure music will bring you. You are always popular and sure of a good time. And there is no easier way to earn money. e Learning to Play Made Easy We now furnish free with every Wurlitzer instrument a Special Scholarship in a nationally famous school of music. This school has taught thousands to play by a special home study method. Many of its duates are successful professional musicians. ether you wish to play for pleasure or for rofit, choose your favorite instrument and send or this New Offer now! Use the coupon below. - BLE f * ; Free Trial—Easy Payments You may have any Wurlitzer instrument for a week’s free trial in yourown home. No obliga- tion to buy. Payments are arranged in small monthly sums —a few cents a day will pay for your instrument. Sed Free Book for a Illustrates and describes every LY known musical instrament — more 5: es t articles, many of them shown in full colors. Special offers 4 on complete outfits. All genuine Wurlitzer instruments—buying f direct from Wurlitzer saves you. #f > money. Wurlitzer instruments are ff the result of 200 years experience. Praised by masters in every sphere ff of music for artistic quality, rich HY tone and fine workmanship. We also give you our Free Trial, Easy Payment “ee and Free holarship offer. No obligation. Sendcoupon now. » WurRLIIZER Cincinnati New : y @)_Send_ this Coupon > — || The Rudolph Wurlitzer Co., Dept. 1784 117E.4thSt. Cincinnati 329 S. Wabash Ave. Chicago | 120W.42ndSt.New York 250StocktonSt.SapFrancisco Send me your Free Book on musical instruments. ‘Also our Free Trial, Easy Pay: t plan olarship Offer. No obligation.” a Copyright 1925, Rudolph Wurlitzer Co. © This seal on a radio or tool advertisement signifies the ap POPULAR SCIENCE MONTHLY The Home Workshop Bench Drill Press Made of Pipe and Fittings ALTHOUGH made of common pipe fittings and pipe, the small bench drill press illustrated is capable of doing fast and accurate work. The driving shaft is machined from a piece of cold rolled steel. A thrust collar is located at the chuck end and the end is turned to a Morse taper to suit the chuck to be used. The standard tees used as bearings are babbitted to suit the shaft and tapped where convenient to receive grease cups. The faceplate is made from a piece of 14-in. steel plate per- fectlyflatand smooth. A hole is drilled and tapped in the center of plate to fit the end of the DRIVING lifting rod. The aie td rod is cold- rolled steel. The lever block in which the end of the lifting lever slides may be either round or square,with flanges on top and bottom. The lifting levers are made from pieces of )4-in. flat steel. A square hole in the levers engages a fulcrum shaft, which passes through a pipe cross. A rod is connected with the back lever and passes through a hole in the bench to a treadle underneath. This foot method of feeding the faceplate upward allows both hands to be free. The pulleys are of cast iron. A selection of speeds can be obtained, of course, by using a pair of step pulleys.—F. N.C. - FTING RODS Details of simply made bench Mercury Improves Friction . Contacts in Radio Parts O OVERCOME the tendency of the rotor shafts of radio condensers and couplers to oxidize and cause a loss of efficiency in instruments designed to use - friction contacts in- g HOLE IN stead of “pigtails,” BUSHING some radio fans who pride themselves up- on their neat work- manship use mer- cury to insure good contacts. The method is__ illus- trated. A groove about 1/16 in. deep is filed around the shaft so that it will be inside the bushing when assembled. A %-in. hole is drilled in the bushing to coincide with the groove. The shaft and bushing should be absolutely clean. When assembled, the groove is filled with mer- cury by means of a pipette or medicine dropper. This insures good conduction.— PHILIPPE A. JUDD, Portsmouth, Ohio. GROOVE FOR MERCURY An improved condenser bearing 1 USED THAT HUNTING THROUGH THE SUPPLY OF TOOLS FOR AWRENCH ~- THAT Wice FIT hs It Looks Funny —but it isn’t—when you're far from help ERY likely means an expensive tow-in job—which would cost a whole lot more than a selected Set of Snap-On Wrenches that would always be on hand to help you out of trouble. Spring is in the air—the open road is calling. Play safe this season—go over your car and tighten up all the nuts and bolts before you start on a trip. It’s a quick job with Snap-Ons, Take your Set with you and relieve that gnawing anxiety about road trouble. It will bring a new ele- ment of safety that will enhance the pleasure of motoring. . * This selected Set for the Ford is equipped with a chart of great value to the owner in making repairs. Ask us about the selected Set for your car. Snap-on INTERCHANGEABLE Socket Wrenches Snap-Ons are the choice of over 250,000 ga- rage mechanics. Look for the name—with- out it no wrench is a genuine Snap-On. SNAP-ON WRENCH CO., MFRS. Milwaukee, Wisconsin Motor Tool Specialty Co. Distributors 14 E. Jackson Blvd., Chicago Send me particulars. My address is— proval of the INSTITUTE OF STANDARDS. See page 25.

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Iny ou’ re ensive 1 cost ed Set would out of n road on—go all the t ona p-Ons, relieve t road w ele- nce the 00 ga- —with- ap-On. AFRS. sconsin na ak Co. ~hicago ess is— Home Workshop cpring Overhauling Lengthens Life of Your Heating Plant By Orion O. Oakes Heating and Ventilating Engineer § SOON as fire is no longer needed in the spring, clean out thoroughly all flues and the upper portions of your steam-heating or hot-water boiler with a wire flue brush. Rub all surfaces well to remove soot, ashes, and seale. Part of this material will fall on the grates, part will be drawn out through the various cleanout doors, and part will lodge in the smoke bonnet. When the flues and upper works are well cleaned, remove all the ashes from the ash pit and clean the pit. The smoke pipe should be removed and scraped with the flue brush, and the smoke bonnet, which now will be accessible, should be freed of all accumulations. Next obtain a plant sprayer or oil gun and spray all the interior surfaces of the boiler with crude oil or light machine oil. SMOKE PIPE REMOVED AND BONNET FREED OF ALL ACCUMULATIONS VASELINE GREASE AND RAGS {§ After being thoroughly cleaned, all metal surfaces are sprayed with oil or greased If convenient you may use oil taken from the crankcase of your automobile for this purpose. For the exterior portions use vaseline or a light grade of automobile grease applied with a rag. The importance of this work is because all flue doors, fire doors, clinker doors, and cleanouts are ground on the edges at the factory to make contact with the frames. When these ground joints are unpro- tected during the summer, the moisture of the air forms sulphurous acid by com- bining with soot and this in turn acts on the cast-iron or steel surfaces with a cor- rosive action. When ready to be used in the fall the doors will be found coated with scale and the hinges and pins may be so affected that the close and accu- tate contact of the parts is destroyed. The condition becomes worse each suc- ceeding year. One of the most important requirements for efficient operation of a fire is that all door openings or joints of any kind fit tightly. It will be seen that ill fitting, corroded doors mean poor combustion and loss through fuel waste. If the boiler is of the metal jacketed type, the entire outer surface should be coated with grease. Treat the smoke pipe in the same manner as the inside of boiler and store it in 2 dry place if possible. (Continued on page 116) a POPULAR SCIENCE MONTHLY © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. A new tool that radio fans have been waiting for OW the radio amateur can “wind his own” as quickly and as expertly as any professional coil winder—and at one- tenth the cost. This Goodell-Pratt Coil Winder is a new tool made especially for winding tubular coils, inductance coils, and transformers for superdyne and neutrodyne circuits. Holds any cylinder of cardboard, bakelite, or fibre up to 434 inches in diameter and 7 inches in length. The outer aluminum driving disc is adjusted to the cylinder length by a sliding collar, which can be locked at any point on the spindle with a thumb screw. The outside face of this collar is cut at an angle, afford- ing a cam action against the button on the disc hub, which exerts a continual tightening effect on the cylinder. And because both discs are cone-shaped, the cylinder is centered automatically. The spring wound around the spindle prevents it from turning backward and releasing the tension on the coil wire. If unwinding becomes necessary, merely raise the loop end of the spring. Nicely finished in red and black enamel, and natural aluminum, with all exposed steel parts well polished. Length over all 1414 inches, weight 3 pounds. Other tools for radio builders. Write for special radio tool folders, which show all the Goodell-Pratt radio tools, many of which are new and exclusive Goodell-Pratt inventions. GOODELL-PRATT COMPANY, Greenfield, Mass., U.S. A. Makers of Mr. Punch oe 69 5 Coil Winder er = Pa le | z ye a Ae 1500 GOOD TOOL

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116 POPULAR SCIENCE MONTHLY S-E-L-E-C-T-I-V-I-T-Y To A New Degree IMPROVED | MICROMETER DIAL U. S. Tool Condensers GAIN in the van as a result of con- ) stant research and painstaking ex- FACTORY perimenting—U. S. Tool announces an GUARANTEE improved micrometer dial, a boon to radio reception and a new degree in the — selectivity of DX stations. U. S. TOOL COMPANY, INC. 127 Mechanic St. Newark, N. J. Mfrs. of Special Tools, Dies, Jigs, Automatic Machinery and Sub Presses t The separate knob turns the ENTIRE rotor Write slowly, accurately, too precisely to slip by any station within reach. Stations passed by on ordinary for condensers are instantly detected with the microm- . eter dial. Factory-tested and guaranteed to be Literature within 3%, plus or minus, of the indicated capacity. rS) ( ra \@ 4y Ole Evinrude : * : - iy & 7 “Ends All Pump Troubles There is not a single moving part in the new Elto Pump. Yet a flood of water flows constantly through the cooling system. It never fails. The rudder openings scoop up the water as the motor runs, straining it to keep out clogging materials. The whirl- ing Propeller Blades push and force the water into circulation. Once started, the water siphons continuously. Works Perfectly at all Speeds—and in all Waters Slow downtoa fish-getting trolling speed, or open up the throttle wide for a race; go anywhere in muddy or sandy water—fresh or salt. As long as your engine is running, you know the Propello Pump is working. No more sticking valves. No more clogging pipes. No more over-heated engines. No more expensive repairs. Other Elto advantages are 60% More Power, Much More Speed, Least Weight per Horse Power, Instant Starting Every Time, Push Button Reverse, Safe other Steering, Larger Bearings, Sturdier Working Parts, Longer Life. Write for catalog. ELTO_ OUTBOARD MOTOR CO. Ole Evinrude, President Dept.W, Manufacturers’ Home Bldg. Milwaukee, Wis. Ole Evinrude's New3 H.P Fast yInvention (Continued from page 115) The boiler should be filled completely by adding water to that already in the boiler and not by emptying and refilling The water in the boiler has been repeat. edly distilled and therefore has less action during summer than new water. Oil or grease all moving or Wearing parts of the pressure regulator and cove if desired, with an oily cloth to prevent the accumulation of dust through the summer. If there is a thermostat, wipe it and cover with a cloth. Biscuit Pans as Receptacles for Small Hardware RDINARY 10-cent biscuit pans, painted black with screen enamel to prevent rust, are excellent containers for small hardware, such as screws, nuts, tire valves, and washers. The pans may be SS ANGLE LS eS SLIDES ee |) ve = WOODEN —=S The biscuit pans slide on runners placed under the bench top or under any shelf hung to the bottom of a shelf or bench on runners bent from 18-gage galvanized sheet iron, or made from \ by 1 in. strips of band iron and 1-in. square wooden spacers. The runners should be screwed, not nailed, in place.—R. C.T. A Large Glue Scraper Made from an Old Hand Saw A PLAIN wood scraper about 4 by 10 in., made from an old saw, preferably a stiff one, is very handy in knocking off the hardened excess glue from joints pre- paratory to planing, scraping, and sand- papering large surfaces such as table and counter tops. It does not bruise the sur- face and is so large that ample elbow grease may be applied.—J. A. H. Belt Pulley Fastened to Auto with Ordinary Wheel Puller CAR WHEEL ISHING to use my al- tomobile for power SET= Zr. ’ purposes, I fas scREW / MNV/)\ \\ ==\ tened a pulley to a rear wheel by PULLEY WHEEL PULLER means of an ordi- nary wheel puller. A wooden pulley " ‘was sawed out to the right size to give the speed de- sired. This was fastened to the wheel puller with the setscrew. I jacked up the rear end of the car, screwed the puller on the hub, turned the pulley to a smooth finish, and belted it to a saw.—S. H. 8.

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may be “ae placed - shelf bench on Ivanized by 1 in. . Square hould be R. Cy Made aw ; 4 by 10 referably eking of yints pre- nd sand- table and > the sur- le elbow [. . Auto Puller ING to > my ale for power I fas- pulley to vheel by an ordi- el puller. len pulley »d out to t size to speed dee the wheel ced up the puller on a smooth Ss. H. How to Re-Cane Chairs (Continued from page 96) it in the groove. Then pour more thin, hot glue into the groove, making sure that the entire length is covered and that there is a surplus amount to be forced out as the spline is driven into place. Take one end of the spline, which has peen soaked previously in water to make it pliable, and drive it in at the center of the back rail. Tap it lightly all the way around until it meets in the back. Cut off the surplus with a saw or sharp chisel. While doing this, put a block under the end. Avoid scratching the chair. With a narrow wedge or a small block of wood, drive the spline down into the groove all the way around until it is flush with the suriace of the chair. Wash off the surplus glue carefully with hot water. After the cane has dried thoroughly, which will take two or three days, it will be as tight as a drum head. If you have been careful to get an even tension on the surface when driving in the wedges, the surface will be entirely free from wrinkles or puckers. The chair now is ready for use, but to make sure that the cane will remain taut in various temperatures, it is well to give both lower and upper How the strand ends are tied surfaces several coats of good white shellac, after which varnish may be applied. If the chair you are to cane has no spline and, therefore, has been woven by hand, a different procedure is necessary. The diagrams on the preceding page give the correct method to follow. Cane for hand weaving may be pur- chased by the hank of 1000 ft., and comes in various sizes such as fine-fine, fine, medium and coarse. The medium size isused most. You will need about 300 ft. for one chair and about 5ft. of binding cane. After removing the old cane by running a sharp knife or chisel across the strands on the bottom and lifting it out from the top, clean up with soap and water and a good stiff brush. All cane is moistened for not more than three minutes before using. While the diagram explains the steps in caning a Square bottom, the method is the same regardless of the shape. If the chair is wider in the front than at the back, count the holes at both places. Say there are 17 in the back and 19 in the front; start your caning from the left rear hole and go to the second hole in the front. If there were 15 holes in the rear rail and 19 in front, you would begin in the left rear hole and go across to the third hole in the front rail. For circular Seats the point to keep in mind is to have your cross strands parallel. Referring to the diagram (page 116), Tun one end of the cane first through A about 2 in. and hold it with a peg. Run ———— (Continued on page 118) Ritchie © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. POPULAR SCIENCE MONTHLY iF ofn fairness to your family and yourself F course you want your family to enjoy all of the ad- vantages of modern living. But, have you provided them with the modern way of writing? Have you considered what a wonderful help a Remington Portable will be to that boy of yours, and what an invalu- able training it will give him for his life’s work—whatever it may be? Do you realize the many precious hours it will save for everybody in the home? Wouldn’t it be worth a great deal to you to have this always ready helper on hand to take care of your personal writing? Countless homes now find the Remington Portable indispensable, and we are sure that yours is no exception. The Remington Portable is the choice of most people the : world over, because it has every feature common to the We believe we waboh hess big machines, is easy to operate, does beautiful work always, typewriter rib- is compact, and carries its table on its back. bon inthe world S ‘ " ed deans Sold everywhere. Easy payment terms, if desired. Write is PARAGON today for illustrated “For You, For Everybody.” Address Department 67 REMINGTON TYPEWRITER COMPANY 374 Broadway, New York Remington Portable THE RECOGNIZED LEADER IN SALES AND POPULARITY Oe “ye

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118

South Bend

POPULAR SCIENCE MONTHLY UseYourLathe Now You Can Get This Quick Change Gear Lathe Screw Cutting

—for only *284. Easy Payments if Desired Here is your chance to get a brand new, latest improved South Bend Lathe on convenient terins. We ship Lathe upon receipt of first payment, allow 30 days’ trial, and you have the In this way it helps earn its We make this liberal offer on any South Bend Lathe. 31,000 in use in U. S. and 64 Foreign Countries. For example, in plants of 2 largest Steel Companies, 8 largest Auto Factories, 5 largest Railroad Shops, by U. S, Government, etc. use of the Lathe while paying for it. own cost. SOUTH BEND Lathes embody 32 major im- provements made within the last 2 years. Unsurpassed in accuracy and efficiency. SELES AE

SOUTH BEND LATHE WORKS, Q CATALOG FREE! Write or send cou- 317 East Madison St., South Bend, Ind. a pon today. Free Book Gentlemen: I would like to know your : shows 96 styles in all sizes, from small Bench Lathe to largest Factory Lathe. Compare our prices with what price and terms on a............ Lathe. ff others ask, and remember every South Bend Lathe Please send Free Catalog. | carries our liberal guarantee and 30 day trial offer. Send for Catalog today. eGR vices amine Subnomse ene E } 317 EAST MADISON STREET, CE Pe Pee EOL EE oe ~ South Bend Lathe Works, SCUTH BEND, IND., U.S.A.

EasytoDraw Cartoons When Shown in the RIGHT WAY Some of the cleverest cartoonists and comic artists learned how to draw in their spare time by robowing Cartoonist Evans’ Simple and Easy to Learn Metho and are now MAKING GOOD MONEY. Send one of your drawings, and let Mr. Evans see if you have ability and receive the Portfolio of Cartoons and full details about the course. It is not expensive. THE W. L. EVANS SCHOOL OF CARTOONING 825 Leader Building Cleveland, Ohio

A GM é Adds as rapidly and accurately as a § _ machine, yet fits the vest pocket. i 95 s Mechanically perfect. Easy to operate Bae . —_———_ —

—nothing to get outof order. Everyone & who uses figures should own one. Counts Up to 999,999,999 Total visible at all times. A pull of the finger clears it. Don’t carry a pocket full of pencil stubs and — paper to do your figuring, a a Ve-Po-Ad. 4 end no money. 10 Days Trial Fea.ameant o. dress and we will send machine my Pay postman on delivery $2.95. Use it for 10 days to prove it does all we claim. If not perfectly satisfied we willrefund your 4, money. Limited supply. Send order todaye Reliable Adding Mach.Corp.,Dpt, 75, 170 a Washington St., Chicago, Ia, ere’s @ money maker. Everybod: wants one, Splendid profit. "Writs for special offer.

4 are the latest and most modern in existence. A. G. Mohaupt, Radio Engineer,

’ Become a big-pay man in the greatest industry of alltime. Quickly, easily and right at home, you can fit yourself for highest salary positions, or you can cash in on your sparetime. The callis urgent for mechanics, operators, designers, inspectors. Unlimited, fascinating opportunities on land or sea train YOU at HOME ce ARADIO EXPERT Under my practical, easy to understand, instruction—you qualify in an amaz- ingly short time. No previous experience is necessary. Every branch of radio becomes an open book to you. You learn how to design, construct, operate, repair, maintain and sell all forms of Radio apparatus. My methods FR EE Wonderful home construction tube receiving set of the latest design. RADIO ASSOCIATION OF AMERICA, Dept. 44, 4513 Ravenswood Ave., CHICAGO

| ATA Write Today..." FREE

© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. April, 1925)

The Home Workshop Tank for Cheap Sprayer Made from Oil Drum <| A STEEL drum such as may be haq | at low cost from almost any garage can be made into an efficient sprayer tank for poultry yards, orchards, and gardeng Pipe fittings with a hose and suitable shut-off nozzle are attached to one of the openings of the drum. Through the cap or plug of the other opening a hole jg

A homemade spraying tank for use in the garden, orchard, or poultry yard drilled to admit an auto tube stem. This stem is attached with suitable gaskets so as to be airtight. After the drum has been filled with the spraying mixture and placed on a flat wheelbarrow, so that it may be rolled occasionally to keep the mixture agitated, an auto tire pump is connected with it and used to obtain sufficient pressure for spraying.—GEORGE G. MCVICKER.

How to Re-Cane Chairs (Continued from page 117) across and down through B, and hold with a second peg. Move the peg each time to insure tightness, but through the whole procedure do not strain. The diagonals are woven in the fifth step. Start at A and run the strand under the strands woven in the first and third steps and over those of the second and fourth steps. Take great care to follow this order throughout. If the cane does not lie flat and straight, some mistake has been made. Be sure that the cane runs into the squares and not between two strands. Fasten one end (LS) by slipping it under one of the strands on the under side of the chair. Continue as shown, following the holes alphabetically. In the seventh step lay the binding cane X over the holes and bring the medium cane Y up on one side and down onthe other asshown. Keep the medium cane pulled very tightly and when you have gone completely around, tie down the loose end under the last loop. If the reader of this article happens to be a boy who is anxious to earn a little money, he will find that almost every home in his neighborhood has a chair stored away somewhere that needs to be re-caned. A charge of $1 for putting m the machine-woven cane and $2 for the hand-woven will be a very reasonable price, yet, after he has gained experience, it will net a nice little sum in comparison to the labor expended.

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, 1925" hold each ‘h the . fifth under third 1 and follow > does ce has > runs 1 two pping under hown, nding g the down edium n you down ens to . little every chair to be ing in or the onable rience, arison ~ Home Workshop Chemistry . Simple Formulas that y Will Save Time a and Money OW temperature can be obtained eas- L ily through the use of relatively common chemicals. Dissolving one part of sodium nitrate in an equal part of water, the quantities being taken by weight, will give an aver- age drop of about 25° C. or 45° F. Equal quantities of ammonium nitrate and water also can be used. The drop in temperature will vary from 50° F. to about 10° F. A chemical reaction will serve the same purpose. Eight parts by weight of Glauber salts (sodium sulphate) are used Mixing chemicals to pro- duce a refrigerant (at right) and making ice in the cold mixture (below) together with five parts by weight of dilute hydrochloric acid, made by pour- ing the acid slowly into an equal quantity of water and stirring it. Let the acid solution cool before pouring it into the container holding the crystals. A double decomposition takes place and ordinary salt, or sodium chloride is formed together with sulphuric acid. By this method ice can be made on a small scale. Into a large container, preferably non-metal because of the acid, place the Glauber salts and add the dilute acid. Into a smaller and taller vessel place pure tap water and immerse the vessel in the freezing mixture. In from five to 10 minutes, ice will be formed. It can be used without danger, for the chemicals used in the freezing mixture do not come in contact with the water in the smaller vessel. Other uses for such freezing mixtures will suggest themselves. Liquids that do not freeze readily also can be prepared. A saturated solution of table salt in water will remain fluid to approximately 0° F. or about 18 degrees below zero on the C. scale. This solution will not corrode or affect the metal parts of an engine. Equal parts of glycerine and water also can be used and it has the advantage of not crystallizing when the water evaporates. In both cases, when the water evaporates, just add pure —— oo: POPULAR SCIENCE MONTHLY Now You Can Afford — a modern precision-made set which “cuts through” ( Tuned radio frequency for distance and selectivity, reflex — for economy, the wonderful loudspeaker tone quality and _ volume which comes with ALL-AMERICAN precision manu- — facture—all are present in this non-radiating three-tube | receiver. & And, owing to the economy of “wiring it your- — self,” Att-AMAx Senior costs less than a finished one- tube set of equally high quality. ( Take it home today ftom your favorite radio store; wire it this evening, and “‘tour | the country” before you retire for the night! Price $42. © All-Amax Sets come completely mounted on panel and baseboard with full instructions for wiring. The RADIO KEY BOOK has, concentrated in its 48 pages, the an- swers to those questions you have been wondering about. Itis a radio education in itself. Send 10 cents, coin or stamps, for your copy. ALL-AMERICAN RADIO CORPORATION PIONEERS IN THE INDUSTRY 2668 Coyne Street ° . ; Chicago , ICAN all wher’ Fon Gikee AU AMERICAN. ag All-Amax Junior There is now an ALL-AMERICAN Transformer for every radio need= Audio Frequency, Radio Frequency and Power Amplifying (Push- Pull) Transformers and Super-Fine Parts for Intermediate Frequency work. A one-tube reflex set that bringsin the locals ontheloudspeaker,with % wonderfully clear tone quality, or tunes them out and gets real dis- tance. Non- Radiating. Price $22.00 Largest Selling Transformers in the World | © This seal on a radio or tool advertisement signifies the approval of te INSTITUTE OF STANDARDS. See page 25.

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POPULAR SCIENCE MONTHLY “I selected it for its high insulating qualities It cuts down the losses in the circuit’’ HOSE were the exact words of a prize-winner in a radio set-building prize contest, when asked why he used a Radion Panel. Like thousands of others, he had found by experience that there is nothing quite like Radion for real results. OUR engineers developed Radion Panels especially to order for radio. Losses from surface leakage and dielectric absorption are exception- ally low. And low losses mean clearer reception, more volume and more distance. Easy to work—moisture proof —resists warping RADION is easy to cut, drill and saw. You need not have the slightest fear of chipping. Radion resists warp- ing. It’s strong. It’s moisture proof. It comes in eighteen stock sizes and two kinds, black and mahoganite. RADIO dealers have the exact size you want. The use of Radion by the manufacturers of ready-built sets is almost invariably a sign of general good quality in that set. Send for booklet, “Building Your Own Set’’ OUR new booklet, “Building Your Own Set,” giving wiring diagrams, front and rear views, showing new set with slanting panel, sets with the new Radion built-in horn, lists of parts and directions for building the most popular circuits—mailed for ten cents. AMERICAN HARD RUBBER CO. Dept. F4, 11 Mercer St., New York City Chicago Office: Conway Building Pacific Coast Agent: Goodyear Rubber Company, San Francisco, Portland RADION The Supreme Insulation © PANELS Dials, Sockets, Binding Post Panels, etc. AMERICAN HARD RUBBER CO. Dept. F4, 11 Mercer St., New York City Please send me your new booklet “Building | Your Own Set”’ for which I enclose 10 cents l (stamps or coin). ‘Sada Pies on bis ebb wwy son wee siehies 000s Giving Wings to Your Speedster (Continued from page 83) vided. The advantage in removing the magnets and coils lies in reducing the weight about 35 lbs., eliminating the drag of the magnets through the crankcase oil reservoir, and avoiding the magnetic pull. The brass spools or spacers should be retained on the flywheel so as to splash the oil, unless some additional form of lubrication is added. The engine flywheel and crankshaft should be balanced accurately on knife edges after these alterations are made. There are several types of supplemental oil-circulating systems from which to choose in order to improve the circulation and insure having sufficient oil in the trough for high speeds. These systems frequently are attached to the engine sump or to the petcock holes in the reser- voir. They are connected with a small plunger type of oil pump, driven by the camshaft, which forces the oil to the for- ward part of the engine. Another method that has met with considerable success is to shim under- ee ne” Positively identified by the Ace trade mark stamped on the frame. A few strokes through the discs will sharpen the dullest knife. Try your hardware dealer first or send $1.00 direct to ACE HARDWARE MFG. CorP. \ Philadelphia Chicago San Francisco ) Only $5569 Lig i ‘ : e@month forafewmonths pee | easy toownthefamous ga" saat standard WITTE En- _ im gine. Uses Kerosene, Gee —— Een lasippal Stik eplteniat Soitienedl as, uipp celebra oubl WICO Magneto. Simplest and cheapest to OD= . New device makes stertins iy eae pe ower, 1Ze! - See ew net onteraueyche N RIAL, Write tod lustrated engine book—sent absolutely Five "Nocblicgee wie enn ENGINE WORKS i e Building, - = « AS CI 3928 Empire Building, - - PITTSBURGH,'PAe 2228 Witte Building, - SAN FRANCISCO, CALIF, Another example of a _ skilfully remodeled speedster incorporating engine refinements neath the crankcase lower cover rein- forcement with sheet metal. This has the effect of increasing the depth of oil in the troughs. Care should be used, however, to see that the large ends of the connect- ing rods do not strike. In connection with this method, it is possible to use a 3-in. oil-supply tube and to substitute a larger intake funnel adja- cent to the flywheel. To insure an adequate supply of oil for long runs, a desirable arrangement is to place a 1-gal. oil tank in the rear of the ear. Connect this with a hand pump within reach of the driver and run a small copper pipe from the pump into the side of the breather pipe of the engine. The oil can be replenished at any time with a few strokes of the plunger. The grade of lubricant is important. Only the best grade engine oil of high heat resistance should be used. Castor oil is recognized as a dependable lubricant for high temperatures. As long as a car is driven at moderate speeds, the thermosiphon cooling system is satisfactory. It is too sluggish, how- ever, to combat the increased heat of high-speed operation. Many water-cooling systems are sold. These are engine-driven and increase the circulation as the speed increases. They (Continued on page 121) DON’T WEAR, A TRUSS BE COMFORTABLE— Wear the Brooks, Appliance, the modern scientific invention which ives rupture sufferers immediate re= fier. It. has no_ obnoxious oe pads, Automatic Air Cushions bind and signature of C, E. Brooks which appears on ev Appliance, None other genuine, Full information booklet sent free in plain, sealed envelope. BROOKS APPLIANCE CO., 230-A State St., Marshall, Mich. musical instrument; not toy. 13 in. long. Don’t send a@ penny—just_name and address. arrival of gy 87 free 2. Fe "plus f No talent or experience necessary. Fascinating work. Pays big money. mplete instruction k TE ABOUT: Alphabets, Colors, HOW TO MIX PAINTS, Show Cards, Window Board and Wall Signs, Ready made _ letters, Gilding, TRI OF THE TRADE, my i : cks gives 100 Alphabets and Designs, und in le Imt. leather, gold edges, 0 and four ball bearing Show Card e448 too OziivicPub.Co..87RoseSt. Dept. 72,Newvork | / EARN MONEY /MMEDIATELY~ | / WE FURNISH EQUIPMENT TO START \ ’ Promanco Auto Frames ail the rage! Adjustable. Add 109% to a pearance of any car. Order to ay. Postpai -00. Money returned if not sat- isfied, Distributors. Fortune right men! Demand sp ¥ ing like wildfire! Exclusive territory now. Write dept. 13. PRODUCTS MANUFACTURINGCORP. © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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Giving Wings to Your Speedster (Continued from page 120) ither with the inlet or outlet ee conection and are gear or belt | sive from the fanshaft or the camshaft. In the selection of a water pump, care should be taken to obtain one that may fastened securely at several places to the cylinder block and can be relied upon to stay rigid. This is important, espe- cially in regard to the propeller shaft at the i land. Woe the engine speed in the neighbor- hood of 2000 r.p.m., the weight of the pistons and connecting rods becomes an important factor. Unless the engine is to be fitted with special aluminum or alloy pistons and light-weight connecting rods, the methods of weight reduction illus- =e. « Summary of Alterations that Will Improve Your Speedster IGNITION—Substitute single-spark system or high-tension magneto reg ONS |X Ta LUBRICATION—Increase oil-trough supply you, and add auxiliary oil pump MO, COOLING—Use pump system for circulation } ey PISTONS—Use alloy pistons, or lighten cast-iron pistons by drilling CONNECTING RODS—Drill out webs of the original connecting rods CRANKSHAFT BALANCE—Pistons and connecting rods must be uniformly drilled to maintain equal weight. Balance flywheel exactly, after removing magnets VALVES—Substitute tractor valves 14 in. larger in diameter EXHAUST MUFFLER—Remove present muffler and install straight tubular exhaust WHEELS—Wire wheels are recommended for flexibility; they also reduce overheating of tires GEARS—Three-to-one, or 234-to-one gears in differential permit of higher car speed, without excessive engine speed LUBRICANT—Only best grades of oil, with high viscosity and flash point, to be used trated in the drawings on page 83 should be applied. The weight of the piston is reduced by drilling a series of 34-in. holes between the second and bottom ring and also below the bottom ring. In these locations the holes do not noticeably impair the strength of the pistons and are effective in reducing weight and improving the lubrication. The connecting rod is lightened in the same manner. The smallest hole is 5/16 in. in diameter; the other holes increase gradually to 14 in. They are drilled through the web of the rod. To improve the lubrication at the big end bearing, it is advisable to drill two in. holes into the bearing from above. These conduct a portion of the draining ) oil on the rod to the bearing. It is essential that each piston and con- necting rod be exactly alike in weight so 48 to insure balance. Overhead valve attachments are ob- tainable for use on the Ford engine. These Unquestionably increase the power. It is (Continued on page 122) Be Superintendent of an Electrical Power Plant POPULAR SCIENCE MONTHLY Electrical Engineers This is not a one-man, one idea school. 2 famous Engineers and Executives of the following corporations and uni- versities helped me make Dunlap-train- ing the most complete and up-to-date: General Elec. Co. Commonwealth Edison Co. Crocker-Wheeler Cutler-Hammer g. Co. American Tel. & g. Co. Western Elec. Co. Underwriters Laboratories, Inc. Columbia University Dartmouth College assachusetts institute of Technology University o = cost. Own your own Electrical Repcir Shop, Fixture, Supply or Ape pllance Store ELECTR § give you these 4 Electrical Outfits! You don’t have to leave your home # Or quit your job, you don’t need post- graduate Laboratory courses when you are Dunlap-trained. I send you these 4 costly, complete Electrical Outfits, all the Laboratory and Shop @, apparatus you need to understand fa Electrical laws, theories and principles easily and quickly. Not one penny extra for this equipment. Earn While Learning mq As early as your eleventh lesson, I = give you special training in wiring, = Radio, Electrical repairing, motors, etc, sO you can go out and start urning your instruction into cash. * It’s no trick to earn enough in a # single evening to pay one month’s tuition So you needn’t let lack of ready money or anything else keep you from ¢ this wonderful home-training. Chief Engineer Dunlap, AMERICAN SCHOOL Dept..£-475, Drexel Ave., and 58th St. Chicago, lil. Electric | Ses hy Boss Electrical Con- struction Jobs After you finish my Training! If you’ re now earning less than $40 a week enroll for my home-training in Electricity and I will guaran- tee under bond in writing to find you a position at 50% raise in paywithin sixtydays after you finish, or I will refund every penny of your money. Mine is the only home-study Electrical School to make, this guarantee. $60 to *200 a Week! Enormous demand for all-around Electrical Experts as Power Plant Superintendents, Chief Electricians, Foremen of Construc- tion, Electrical Draftsmen, Radio Engineers, etc. And with my training you can go into business for yourself with little capital and make $3000 to $12000 Business ofa MillionOpportunities While you’re at it, while you’re spend- ing your time and money to be a suc- cess, Train for the big-pay Boss jobs in the world’s fastest growing indus- try. The world’s work is now being done by Electric power. Autos, ships, buildings, aeroplanes, all electric equipped. Electric lights, everywhere. Think of Radio, Telephones, Tele- graph, Electric railways. This busi- ness DOUBLED in the last 9 years, and they say it will double again in the next 6 years! Mail Coupon at Once I have a surprise offer for youl Cou- pon brings complete intormation, free catalog, my sensational guarantee of a 50% raise, and my confidential Mail it right awayl surprise offer. SMERICAN SCH lef Engineet Dunlae ot. E-47S 0 : AMExel Ave. & S8th St., Chicago i t Send me at once complete inform es = i . 4] paren off b eE0%, raise, also your con- ante: fidential SURPRISE offer. IS) This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. Receiving Set

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It’s a Race Not a Run! Topay’s machines make a race of production, not a run. From the new design, new speed-gains; new time-savings. How many pieces per minute will it add to the best records yet? Stop-watch and counter give the answer! How to feed in material—speed out the product—still faster ? Your expe-iments, your improve- ments will tell, and tell exactly in the production-records on a a The large Revolution Set-Back Counter below records the output of any machine where a shaft-revolution — indicates an operation.

Sets ba-k to zero from any figure by turn- ing knob once round. Supplied with from four to ten figure-wheels, as required. Price with four figure-wheels, as illustrated, $10.00—subject to discount. Cut less than one-half size. Set-Back Rotary Ratchet Counter, to record reciprocating move- ments as on presses, $11.50 (list). Smaller counters from $2.00 up. Speed Counter Here’s the handiest instrument for finding revolutions-per-minute of a shaft or flywheel. You hold the tip of the counter against end of revolving shaft; press lightly when the se ond hand of your watch comes to O; release pressure when minute is up. A spring clutch con rols the recording mechanism.

(Cut less than 1} size.) The Veeder Speed Counter enables you to keep motors, engines, generators, line shafting and machines operating at efficient speeds. Price, with two rubber tips (as illustrated) $3.50. FREE—The 80-page Veeder booklet of counters for all ma- chines and development-work The Veeder Mfg. Co. 44 Sargeant St., Hartford, Conn.

eed

The Home Workshop Gi ving Wings to Your Speedster (Continued from page 121) possible to improve the engine, however, without this expenditure. Ford-tractor valves can be used in the ports, increasing the valve diameter 14 in. This amount must be removed from the valve ports; that is, the diameter must be increased 14 in. For this purpose it is sometimes pos- sible to use a sharp valve-seat reamer, grinding down the reamer to obtain the size. It is obvious that these valves must be ground to a perfect seat. The back pressure caused by the use of a muffler decreases the engine power and is to be avoided. One successful method of accomplishing this is illustrated. For open road work the cap is removed. Wire wheels are recommended as repre- senting the most desirable change from the wooden spoke type. These wheels have elasticity and exceptional strength. The heat generated by the tires, espe- cially on hot days, isradiated more readily by these wheels and the tir2 temperature is kept down. It is advisable to change the drive pinion and ring gear in the differential either to the ratio of 3 to 1 or to the ratio of 234 tol. It hardly pays to make these gears, as they are obtainable at a reason- able cost. These engine changes are not expensive or difficult to make. They are merely a matter of knowing what to do. The changes suggested embody the result of long experience in making fast cars faster. A tabulation of the alterations under different headings is given elsewhere to aid you in selecting improvements you wish to adopt and in preparing a list of pur- chases to be made before undertaking the work of adding speed to your speedster.

Underslinging a Ford Speedster to Obtain a Racy Appearance ANY amateur mechanics who have converted their light cars to the speedster type by the removal of the regulation body and the installation of Ll S ANGLES V4 THICK REAR SPRING SUPPORTS FRONT AXLE

y FRONT SPRING So How the front and rear springs are lowered without making any elaborate alterations SPRING BRACKET bucket-type seats, large gasoline tank, and rear tool-carrier, are disappointed in the general appearance. The elevated frame seems top heavy. To lower the frame 2 or 8 in. insures a (Continued on page 123)

Patented Comfort Fea- , ture,which combines ab- * solute comfort, perfect trousers support, and ‘ank Cartridges obtainable everywhere. “g Price SOc. Superior ality x tpaid, ‘ Blank Cartridges, by express, 50c per 100. Johnson Smith & Co., Dept. 331, Racine,

n of whole num! 5 mixed numbers and decimals. ore root end wer. ve Logs and Tangents. Made o! scales on white celluloid. Size 4 in proved and adopted by colleges. with Instructions, $1.50. 60c extra. Sent C.O.D. if,

spe ref pli det

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+ 1m TOL Ce 190 ee MN = & a soe.

| er April, 1925

The Home. Underslinging a Ford Speedster (Continued from page 122) Ek. ‘or appearance, steadies the car, and sal <a wheels to hug the road when making turns at high speeds. In the accompanying illustration a method of accomplishing all this is shown. The supports for lowering the rear spring are made from 4-in. plate, rec- tangular in shape and drilled each end. A rod at each side passes through the plates. One end of the rod is fastened to the regular spring hanger; the other extends to the radius rod, where it is held as shown. When the spring is placed in the lower position, it is necessary to use angle plates as a support in the center. The lowering at the front of the frame is accomplished by moving the axle forward and making a bracket of rec- tangular section, with two holes drilled through each, to support the spring. The forward hole of each bracket is engaged by a bolt through the axle where the spring perch previously was located. The rear hole is used for fastening the spring perch above the bracket and the radius rod below the bracket as detailed. The moving of the front axle forward also lengthens the wheel base. This is de- sirable, as it increases the steadiness with which the car holds the road. In fitting the forward bracket, the builder should make the upstanding lip, shown on the bracket, bear against the axle. This is to insure perfect lateral rigidity of the front axle. Inexpensive front radius rod braces are obtainable, their use depending upon the distance the spring is moved to the rear.

Reforging Front Axle Lowers Car’s Center of Gravity

(y= ingenious amateur mechanic who was converting his light car into a speedster, lowered the center of gravity several inches by having the front axle teforged as shown. This was accom- plished without altering any essential details or the steering method.

Remodeled ‘‘Flivver’’ Does 94 Miles an Hour on Beach

HAT a remodeled Ford can do was . Shown when this car ran at 94 miles an hour on Muriwai Beach, New Zealand. It is owned by Stanley and

Ivan Andrew, of Auckland.

© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. POPULAR SCIENCE MONTHLY 13

Pll Fix It! NOTHING could be simpler with these Klein Pliers. Fact is, I’m glad to get my hands on them again. I guess every man feels that way about good tools. Yes sir, most men do feel that way. That’s one reason why Klein Pliers have been the favorites for 68 years, You'll notice that most hardware stores feature them. Electrical companies specify them! Treat yourself to a pair today. by & Sons 3

r\ © Mathias NW \ey

ID you ever look the tube ques- tion square in the face? Ever stop to realize that the vacuum tube will make or break your receiving set as far as good results are concerned? Give your set a fair chance to bring in the distant programs. Resolve now that a good set deserves good tubes and decide on MAGNATRONS. The results will pleasantly surprise you. MAGNATRONS know no superiors. And yet the MAGNATRON DC- a 201A, the MAGNATRON DC-199, scree) | | 5g and the MAGNATRON DC-199 with Lo | | large base sell for only $3 each, at . or your dealer’s. Connewey Electric Laboratories New York, N. Y.—Manufacturers ATRONS

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We’ve mapped the air for Radio explorers! Get your copy of this great new map to-day WIST the dials until you catch a faint hum. Nurse it carefully and it becomes a murmur of distant music. Then a moment of silence. ‘This is station KFAF, Denver’”—and you add another station to your list. But how far away was it? What sort of country did the message flash over? You want to visualize your exploit and mark it for future reference. You can—with the New Collier Radio Map of the United States and Canada. It’s beautifully printed in three colors. Every station is clearly marked and the time zones outlined. Instantly you can tell how many miles away a station is. Cut out the scale of miles provided and paste it on card- board. Put a pin through one end at the point where you are located. Swing the other end across the country until you reach the station you are after. Here are some more points worth noting: 1, If you use a directional aerial, you can pick out any station you want to get on the map, and point the loop towards the exact point where the station is located. 2. Around the map there is an alpha- betical list of all stations which also gives the name of the operator of each. If you miss the letters i | given by an announcer, you often catch the name of the operator of a station which can then be located by referring to the index. 3, The map outlines the boundaries o . . . . . . of the radio districts, identifying them by number. This will be a help in locating amateur stations. There’s a lot of satisfaction in radio exploring with this great new map. And it costs only a quarter. Get your copy at your newsstand, bookstore or radio dealer’s tonight. Or just mail 25c in coin or stamps with your name and address to us direct. P. F. COLLIER & SON CO. Dept. R.M. 250 Park Avenue NEW YORK CITY POPULAR SCIENCE MONTHLY Repairing a Porch Column THE high cost of lumber has led to the use of much wood for the ex- terior woodwork of modern houses that does not last very well. For that reason the home worker often finds it necessary to repair porch steps as described last month, or even to patch porch columns. If a column has rotted away at the bottom, break off a piece of the base molding and base block to allow you to measure the exact size of the block and the diameter of the column. Also find the length of the new base and short length of column required to replace the decayed portion. Have a woodturner make the new section of the column unless you yourself have access to a lathe large enough for the work. Be care- ful to have it made a trifle larger rather than _ smaller than the old. If it should be smaller, a neat repair could not to the column to keep it plumb when it is being cut. Measure exactly the combined height of the base block and umn and mark where the old column is to be cut. Nail on the column two strips to guide the saw, as shown; they must be quite level. If your saw is sharp and fine and the end of the new piece of post jg =a we rut i= || | — a LI | 4 Sawing out the decayed base of a porch column before inserting a new piece be made, but if it is a trifle larger, it is easy to pare and sandpaper the joint down and make a workmanlike job. It will be necessary to prop up the porch roof with a strut, as illustrated, to take the weight off the column. One or two braces may be nailed from the house Holder for Razor Blades or sharpening steel knife may be brought to akeen edge by drawing it over the of a hacksaw. The hacksaw blade, which should be of the common type that is hardened throughout, must be held taut in its frame.—T. G. L. Not the least of the many small and sometimes annoying problems met by a busy housewife is to find a‘safe way to dispose of used razor blades. She dare not throw them away, for bare little feet may find them. From bitter experi- ence I found it un- safe to put them in the trash to be burned. Nearly at my wits’ end, I finally thought of cutting a slit large enough to admit a blade in the top of a used evap- orated-milk can. The sharp edges are turned in and the can is enameled white. Once inside, the blades are beyond causing an accident. —MARGARET CRAGO, Louisville, Ky. Renewing Pump-V aloes failed to raise water. valves were worn out. temporary repair at once, I peel weigh from as pvmps often give it is impossible to wait for regular valves. —F. X. ALLEN, Del inne ae ; the new workin the inside of an old auto tire, placed them under a ten them out, and the next morning made valves short length of col. turned true, the joint should re quire no fitting. The base block, however, will have to be fitted to the bevel of the porch floor, although this may be but a trifle, Repair the porch floor under the column, if de cayed, and paint all joints before putting place. Only a few wire finish- ing nails are required to hold the new base in place.—A. E. E. WHEN a stone is not at hand, a back or upper edge FIvE years ago a pump used in con- nection with a rather deep cistern I found the leather Having to makea ed three layers from t overnight to flat- them. They are doing service yet. The service they have given already is more than might be expected from the best quality of leather valves, 80 that this type of repair can be recom- mended, especially out at a time when Rio, Tex. | | of t cate ther 1 ir leav ope’ shet this eith wor! ing easi cur dov in Tn tal lay sti tS] This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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ago a n con- h a cistern eather nake a ; once, s from 1 auto nder a o flat- d the valves y are > yet. they lready might from lity of 2s, 80 recom: ecially . when ralves.

7 ONE great aid in SPECS | kcoping a home Closet shipshape is a con- venient place to

ay the extra leaf or leaves for the sont table. A closet for this pur- usually can be built into the wall in the kitchen entry, hallway, or elsewhere. To make such a closet, find out by tap- ping the plaster or wallboard where two

of the studs or upright supports are lo- cated and then cut out the wall between them from the baseboard up to a height 1 in. more than the length of the table leaves. Make a rectangular box to fit the opening, using 34-in. sides and ends and a sheet of iron or tin for the back. Nail this in place in the opening and finish either with trim to match the other wood- work in the room, or with any small mold- ing that is at hand or can be obtained easily. The table leaves are held in place in the cupboard by dropping a rod with two down-turned ends into screweyes placed in each side of the cupboard.—T. F. Wait, Storm Lake, Ia.

A PUTTY-LIKE mikx- ture of oxide of iron, coal tar, and boiled linseed oil may be used in repairing leaky gutters, water tanks, iceboxes, and the like. Several layers of cloth strips coated with this mixture make a good emergency sub- stitute for a soldered sheet-metal patch. Paste for Stopping Leaks

Dollars for Ideas IN KEEPING your home §ship- shape, you cften hit upon in- genious, time-saving, labor-saving and money-saving ideas. If you will describe, in not more than 200 words, each cf your in- genious keeping-the-home-shipshape methods, we will pay $2 for every one published. Include a_ pencil sketch or photograph to _ illustrate the idea, if possible, and address your letter to the Home Workshop Editor, Poputar Science Montuty, 250 Fourth Avenue, New York.

POPULAR SCIENCE MONTHLY

A set anyone can put to- gether and enjoy all-the- year-’round radio

FOUR TUBE REFLEX AMPLIFIER WITH “DO” CO. TRANSFORMER AND SODION TUBE DETECTOR s~i3

Ae

Directions given so simply that anyone can follow them ABOVE are illustrated the cir- cular of printed instructions and the life-size diagrams of the wiring, which are packed with each Model ‘“S’’ Kitset. Step by step the making of the set is described in clear, simple lan- guage—just simple operations which anyone can easily follow. Sae———= <x Only two tools required—a screwdriver and pliers—and they are included in the Kit.

Enthusiastic praise from Model “‘S’’ user From Hartford, Conn.: ‘‘Just finished it tonight. It’s a wonder. Finest we ever heard. Congratulations for your wonderful engineering.”

CME in for amplification This is the new Model “‘S” Acmeflex Kttset IN THE above wiring diagram special attention is called to the D-Coil radio frequency tuning unit and the vacuum tube detector, giving the famous Acme Reflex (trademark) still greater dis- tance, greater selectivity and better reception. We can save you about $60.00 on this $150.00 radio LF YOU bought this set completely assembled it would cost you $150. But by putting it together yourself you can buy it for only $80, plus cabinet, saving about $60. make it for less but it wouldn’t give results. We could Acme Engineers have done all the engineering for you and have written clear, simple directions which show you, step by step, how to put the set together. Many have done it in three hours, and found it fascinating fun. Even if you know nothing about radio you can put it together. All the parts are in the kitset, even the loop. No antenna to erect. Even a screwdriver and pair of pliers, the only tools you need, are in- cluded. No soldering to do. drilled for you. tubes, batteries, loudspeaker and cabinet. The panel is all The only accessories to buy are And your finished set is the famous Acme Reflex (trademark) now wonderfully selectivity and reception. loud and clear on a loop and loud speaker. sults with other sets of six to eight tubes. tuning dial—easy to tune. improved in distance, It will pull in distent stations Comrere re- Only one Send coupon tcdey for com- plete information. Lots of amateurs have built up a nice business putting together these sets for their friends. Note these features of Model “‘S’’ Acmeflex Kitset Complete directions given for putting set together. No antenna to erect. No technical knowledge or work- shop required. Only two tools and they ere in the kit. No soldering to do. reproduction. tivity. Saves you about $60.00. ACME APPARATUS COMPANY, Dept. P-1, Cambridge, Mass. Pioneer Radio and Transformer Engineers and Manufacturers Only one tuning diel. Excellent Greater distance, sensitivity and selec- Non-radiating—won’t bother your neighbor.

ACME APPARATUS COMPANY Dept. P-1, Cambridge, Mass. Model “‘S” Acmeflex Kitset to:

Send complete information about the new

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writi \ as with the softest lead pencil. The Perfect Writing Instrument 14 kt. gold feed | = clogging. lade of best grade, highly polished, hard rubber, ; s highest class workmanship. , tS : Pocket clip attached makes it a - an instrument of refinement. ~ APH You’ll never use a fountain pen once you try an Inkograph, No complicated mechanism to . clean or get out of order. SEND NO MONEY. “SM Pay postman $1.60 plus postagé. Year’s guarantee certificate - assures absolute satisfaction. Write name and address plainly. INKOGRAPH CO., Inc. Writes with ink free and easy as a lead pencil, with- out a miss, skip or blur. Its steady uniform flow of ink actually improves your hand writing. Won’t blot, scratch, leak, or soil hands, Makes 3 or 4 Carbon

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r]

Page 100

126 All These Included No Extra Charg Set of Sronteg, Instruments sent as soon as you enroll. You get a 20x25 inch drawing board, a 24-inch T square, a 12-inch rule, a supply of drawing paper, two ee. a French curve, pencils, erasers and thumb tacks. They would cost approx- imately $23.00 at any retail store but I include them in my course without extra charge. The Trained Draftsman Earns a Good Salary There is always a demand for skilled drafts- men. Companies are issuing calls every day for men to fill positions paying good aries. Work is light, pleasant and profit- able; a trained d lan can be reasonably sure of having a good job all the time. I Guarantee to train you on practical work under personal supervision until competent as a regular drafts- man, and guarantee, further, to — you meme ne complete working outfit, a spe- Drsfteman cial “Chief sOwn’ draftingtable, and a e instruments you n just as soon as you become my student—all to be included in the course without extra Practical Training Good Salaries I am a practical Chief Draftsman. I have been doing drafting work for a quarter of a century and I know just the kind of trainin that is oo. — men who get po heed aries. in you by giving you a ‘ practical work, the kind” you must be able to do to hold a permanent position. Heater $90) Prt In addition to my other offers, I have made arrangements whereby you may earn a reg- ular drafting course while you are my student. I want to do g possible draftsmen for the urgent calls Chief Draftsman Dobe, Div. 13-64 1951 Lawrence Ave., Chicago, Ilinois Without obligation on me whatsoever please mail your . “Successful Draftsmanship”’ and full particulars of your liberal ‘‘Personal Instruc- tion” offer to a few students. Book is to be sent free and prepaid. Name. —— Senne ‘. Addrese asin saabnc Post Office orc POPULAR SCIENCE MONTHLY Using an Electric Drill in a Planer A portable tool 1s clamped to the clapper block to do the work of a big radial drill By William G. J. Thompson ECENTLY in the shop where I am R employed, a 1200-lb. cast-iron roll about 6 in. in diameter and 10 ft. 6 in. long, had to be drilled. It had 11 grooves, in each of which 15 holes were to be drilled and tapped. Ifa radial drill and chain block had been available, this might not have been much of a problem, but all the regular drill presses were in such a position that a chain block could not be hung in a convenient place to take the weight of the casting. The foreman was about ready to use one of the drill presses and about 6 or 8 men to move the roll, when I thought of adapting a big planer as a drill press. Getting an elec- tric drill from the tool crib, I found that I could unscrew one of the handles and make a holder for the drill that could be clamped in the planer. The foreman, when he heard my suggestion, told me to do whatever was necessary. I obtained a piece of 114-in.-square stock 9 in. long, and had the blacksmith bend it to form a right angle, one leg 714 in. long and the other leg 11% in. I centered the short end and turned and threaded it to fit the tapped hole in the THREADED Drilling a large grooved roll with a port- able electric drill fastened in a planer drill motor casing. Then I screwed the holder into the casing and, finding it wag not in line with the drill, I squared off the shoulder of the holder until it was exactly parallel to the motor. After clamping it to the clapper block of the planer, I found that when the drill was fed into the work, the clapper block would swing out because the drill was ahead of the center of the clapper box, To overcome this difficulty, I locked the clapper block in the clapper box by drilling a hole in the clapper box and tap- ping it for a set- screw. I spotted the clapper block with the drill point to allow the set- screw point to hold firmly. Then I set the drill up and shimmed it until it was per- fectly straight both ways. I locked the clapper block with the setscrew and moved the planer until the first hole was in line with the point of the drill. After drilling this hole, I in- dexed the next groove and drilled the second hole, continuing until the first row of holes had been drilled around the roll. Then I moved to the second row of holes and did likewise until the entire 165 holes were drilled. Thesaving of time and money was considerably over any other method that might have been used. Bench Testing Centers HE bench centers shown below are designed for use in the toolroom for laying out and testing work. The tool can be made at small expense. The base is of cast iron and the centers are of tool steel, hardened and ground. RAD phn rey rs = | Ai . Lie 1 MIs = b—- 12 —-4 |. }-_—____—— 3k a ; Ba = li \_* eT a Gees = fr : (TAIL AND HEADSTOCK —>- CENTERS DEVELOPMENT OF CAM Details of the centers. One pattern serves for both headstock and tailstock castings One pattern will do for both the head- stock and tailstock castings. The slideway runs the entire length of the base. The tailstock and headstock, each of which is provided with a gib, can be set quickly any distance apart and held with thumbscrews. * center and two others about 3 in. from All of the machine work should be done carefully, and for very accurate work the top surface of the base should be scraped. Both centers should be exactly the same height and precisely parallel with the slide and top of base. A cam withdraws the tail center from the work with a half turn to the right. A coilspring returns the center to its position with another half turn of the knurled handle. Double-Acting Machine Clamp Fok machining a large number of straight edges ¥% by 13% by 24 in., the writer had a double-acting clamping fixture made as_ shown. The work-holding casting is 25 in. long, provided with one clamp at the eachend. Much hard work in setting and blocking up often can be saved by the use of a clamp of this kind.—F. N. C. : ‘© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. ON $1 is WO! Wh worn old 1 new ¢ pens, hand wher Jathe To mec quire strug slips ods, battl plent siasn Vit wone screv knoc ing t prot by sf unde Hov ep ‘y Larg gran mett thei cial] sho} they evel sket of 5 the lim: dra anc aro Wi in ¢ a

Page 101

nt ld he pT th he ith til in- he rst nd nd he ng rer ne he ad. me he 7m on ed

Old Bill Says— OME of our customers will spend S $100 repairing an old machine that js worth only $10 as junk. What economy is there in repairing a worn or broken part or replacing an old machine that can be replaced by a new one for the same or, as often hap- pens, less cost? Be sure to use a handle on a file when filing in a lathe. To be a good mechanic re- quires a constant struggle against slipshod meth- ods, but half the battle is to have plenty of enthu- siasm for work.

Old Bill, machine- shop foreman Vinegar is a wonderful help in loosening a rusted screw. When you knock your shop, you knock yourself. If things never are go- ing to suit you, why not get out? protect the ways and bearings from grit by spreading an old newspaper or cloth under the wheel.

How to Draw Accurate Freehand Circles on Shop Sketches —_— + aR a tener ee a ae Pai x | ar: \ H VU | ee HM

Large-scale dia- gram to show ~ Tid method of draw- ing circles

Pie ,VEN experienced draftsmen often make sadly misshaped circles on their freehand sketches. They are espe- cially apt to do so when they go into the shop to draw details, because usually they have not their drafting instruments. Circles can be drawn quite easily, how- ever, without any other aids than the sketch pad and the pencil. Tear off a strip of paper a little longer than the radius of the circle and on it check two points to limit the center and circumference to be drawn. Hold one point on the center and mark several points at intervals around the circumference as shown. With these guides the circle can be filled

In accurately.— FRANK W. BENTLEY. When using a toolpost grinder, always |:

POPULAR SCIENCE MONTHLY 127 BARBERING Now One of the Highest Paid Professions! $90 to *150 Every Week! BE A “WHITE-COLLAR” MAN— Earn $90 to $150 a Week—CLEAN Money!

What's the use of doing dirty, greasy, hard work, when you can NOW make TWICE as much money in a manly pro- fession that is CLEAN, profitable and full of opportunities? | Hil Nt MOLER Graduates ‘ ||| Are Always Busy! MOLER trained Men are always given the preference, for-they alone posse33 the valuable, thorough MOLER training in the application of all the Jatest scientific Barbering methods, includ- ing the Electric hair cutter, the mechanical massage, and Easy to Learn— Quick to Earn! That’s BARBERING for YOU! And the best part of it all is this— scientific barbering, as taught the modern MOLER way, makes YOU a Master Barber a “ad . : e iates vogues in iadie3; ma short course of in. hair bobbing. MOLER also lensive training, al small gives special training in expense! You soon step _ ladies’ a — 2 . easy practical course in the out as your own Boss, if treatment of skin diseases. you wish, in your own “The XXth Cen- tury.”’ — **Orien , Limited’’ and other pheno ene ae nental trains carry I barbers, Shop, which we will Earn While gladly help you equip. : Learning! See the World, ““Where there’s a Will there's Too! a Way” to earn BIG pay! The Majestic, Leviathan, and U.S. Shipping Lines ali carry barbers, Write to the nearest MOLER Colleze, there is one near you, and learn how you can earn while you learn the barber trade. Ask for the new FREE MOLER Barbering Booklet C. Find out HOW MOLER helps you help yourself AFTER ou graduate, as well as EFORE! Find out why MOLER Men are making DOUBLE the money others made _ last year, before Ladies’ Shingle Bobbing be- came so popular. You're NEXT in line for big pay— the MOLER way. Send Coupon TODAY! Or, if you prefer, we will help you step into a real job, with good pay the first day, after you grad- uate. Ocean Liners, crack trans-continental passenger trains, big lux- urious hotels and sky- scrapers all over the world, as well as_ thou- sands of Barber Shops ever where, demand MOLER trained men.

MOLER SYSTEM OF COLLEGES <€<« Address Nearest Branch (Street Address NOT Needed) Please send me without obligation on MOLER SYSTEM OF COLLEGES 30 Branches in United States and Canada New York, N. Y. Cleveland, Ohio Atlanta, Ga. my part your Booklet C. Chicago, III. Detroit, Mich. Memphis, Tenn. N St. Louis, Mo. Denver, Colo. Dallas, Tex. ame....- ee ee ee ee ee ee ee ee ee es Kansas City, Mo. Omaha, Nebr. Houston, Tex. RGU c's'6a:s sinipaind 6 neeeineuweeuaaee Milwaukee, Wis. San Antonio, Tex. New Orleans, La. CAN sot die meteeeas State Cincinnati, Ohio. $25.00 in PRIZE A 9 S |] 65 ! Rew Setgr esas Sells for $1.25. Agent’s Sample 65c.! 2:msco Founsain SCREW CAP PEN RETAINER FITS INTO BARREL ROW-LEARABLEN TS PREVENTING TWISTING OF TUB

See top of page 8 in front of book for details

NON-LEAKABLE

ITS THE POINT. HAS EIGHT GROOVES FOR INK TO FEED Imported from Japan. ‘‘It makes Carbon Copies.’? Guaranteed for 1 year. Hustlers Making $20 Daily! Money refunded if you don’t think it’s the best = you ever wrote with. Up to 150 per cent Profit. Send for quantity price list and distributing plans. F. SPORS & CO., 200 S. 4th St., Lesueur Center, Minnesota

IS] This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

Page 102

128 The pipe-tobacco case is closed for Mr. G. E. M. An open mind is all very well—up to a certain point. But there comes a time when a man tires of experimenting with tobaccos. Particularly, it seems, if he has once known the pipe satisfaction of “‘ good old Edgeworth.” So G. E. M., as he writes, has reached the stage where he is willing to let others do the experimenting while he sticks to his tried and true favorite. Here is his deposition: Larus & Brother Co., Richmond, Va. Gentlemen: After reading some of the letters in the different magazines, written by Edge- worth boosters, I have decided to sing a few words of praise for Edgeworth also. I find it to be the only tobacco giving me complete satisfaction. It certainly is a pleasure to smoke a tobacco with a pleas- ant taste, which at the same time does not bite the tongue. I have tried many brands of tobacco recommended by friends, but have only been able to enjoy one tobacco thoroughly, Edgeworth. Now I take tips on good tobaccos from no one, as I am satisfied in my own mind that there is no better tobacco sold than Edge- worth. is Please put me down as an Edgeworth ster. It’s a smoke fit for a king. Yours rs . E. M., Los Angeles, California, Which proves again that tobacco taste is an individual matter. Two friends may agree on the merits of a book, a play, or almost anything—and at the same time be as far apart as the north and the south poles on their opinions of a tobacco. Let us send you free samples of Edgeworth so that you may put it to the pipe test. If you like the samples, you'll like Edgeworth wherever and when- ever you buy it, for. it never changes in quality. Write your name and address to Larus & Brother Com- pany, 10D South 21st Street, Rich- mond, Va. Edgeworth is sold in various sizes to suit the needs and means of all purchasers. Both Edgeworth Plug Slice and Edgeworth Ready-Rubbed are packed in small, pocket-size packages, in handsome humi- dors holding a pound, and also in several handy in-between sizes. We'll be grateful for the name and ad- dress of your tobacco dealer, too, if you eare to add them. To Retail Tobacco Merchants: If your jobber cannot supply you with Edgeworth, Larus & Brother Company will gladly send you prepaid by parcel post a one- or two-dozen carton of any size of Edge- worth Plug Slice or Edgeworth Ready- Rubbed for the same price you would pay the jobber. POPULAR SCIENCE MONTHLY How You Can Earn Money for Photos of Ingenious Tools OR interesting photographs of time- saving tools and fixtures, such as those shown below, Poputar ScrENCE MontTu_y is making a special offer of $4 each. If you are a mechanic, no doubt you have made at some time or other an especially useful or unusual tool or fix- ture to accomplish work that could not be done so easily with your regular tools. The chances are there was nothing on the market you could buy to serve the purpose of the tool you made, and, although it may have given service only on a few occasions, it probably paid for itself many times. f you have made such a tool, send a clear photograph of it, with a brief description of its construction and purpose, to the Editor, Better Shop Methods Department, PopuLar Sci- ENCE Montnyy, 250 Fourth Avenue, New York. For each photograph available for publication, PoPpuLar Science Montuty will pay $4. Jig for Angle Cock B* USING the jig illustrated, I can machine an angle cock completely in four minutes. The jig is used in center- ing, boring, reaming, counterboring, and tapping angle cocks used on airbrake equipment. The reason the angle cocks are bored is because the threads are worn or broken A simple fixture to hold airbrake angle cocks while machining them in a turret lathe. It increased pro- duction more than 50 per cent off after some service and it is necessary to bore them out to 1 23/32 in. and thread with 114-in. pipe tap in order to screwina 1% by 1% in. bushing. The work was first done in a drill press, but so much time was lost changing tools that I had this jig forged out. cent.—ARCHIE SKINNER, Chicago, IIl. Building Brick Polishes Cast Iron rok smoothing and polishing the meet- ing surfaces of cast-iron doors and hand-hole covers, an ordinary brick is un- It evens up depressions and projections. Ammonia leakages in one case were decreased by its use more than by any other method of smoothing the doors. surpassed. It in- creased my production more than 50 per r1S] This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. On the Deagan Xylorimba Become a crack Xylorimba player right in own home. Easiest instrument to play, F foes one enjoys it—anyone can learn to play it Wi furnish you free 14 complete lessons, Learn ; play in a few hours. Earn $80.00 to $200, 00.2 week. Deagan instruments are world renow ed —used extensively in leading dance, theatre ‘ d concert orchestras, and for Radio Broadcasting Yet the cost of the Deagan Xylorimba op greater than any other good instrument, ry FREE LESSONS—A YEAR TO PAy Our free trial and easy payment plan make it easy to _— at home. —~ coupon below for illustrated literature and details : free trial offer. a se: — — —Mail Coupon Today|—— J. C. DEAGAN, Inc., Dept. 1364 Berteau and Ravenswood Aves., Chicago, Ill. : sees: hye one obligation please send’ me ull information regarding your Free Tri Deagan Xylorimba offer. . a I Your choice of the World’s best typewriters — Underwood, me ington, Oliver—full size, late model, completely rebuilt. and refinished brand new. Prices & % smashed down to half. Act quick. . $2 and it’s you Just send your name and address and we will mail you complete FREE CATALOG prepaid, fully describing an S actual photographs of each beautiful machine in full colors, T every detail of our direct-to-you small-payment plan, Write now for tremendous saving. No obligation whatever. Still time if you act now, international Typewriter Exchange 486-188 W. Lake Street. partment 438 Chicago, i, . Fine Tone $20 Musical Instruments We havea wonderful new copyrighted system of teaching nate music by mail! To first pupils in each locality we will give frees superb Violin, Tenor Banjo, Ukulele, ,Hawaiian-Guitar, Banko, dolin, Banjo-Ukulele, Banjo- Mandolin, Cornet or Banjo-Guitar abso lutely free. Also teach Piano and Orgen. Very small charge for fesvens only, - 3 ae fessons will teac yoo several pieeee, Over 000 success: ers. We © succege charge, Complete outht free. Write today, Dept. 100. obligation, Slingerland Schoo! of Music, 1815 Orchard St., Chicago, lll, ZIP-ZIP "THOUSANDS of boys are 4 made happy with this won- derful Zip-Zip shooter, something every boy wants and never gets tired of. Zip-Zip shooter is _and practically made; boys, if you like hunt ing and outdoor « ports, get a Zip-Zip with plenty of pep and force and learn that quick and sure aim. If your dealer happens not to have them, order vk f from us. Zip-Zip shooter complete 35c or three . 7 for $1.00; send stamps, sit coin or money order. AUTOMATIC RUBS3ER CO., Dept. 22, COLUMBIA, S.C. Ford Runs 57 Miles on Gallon of Gasoline. A new automatic and self-regulating device has been in- vented by John A. Stransky, 26 Fourth St. Pukwana, South Dakota, with which automobiles have made from 35 to 57 miles on a gallon of gasoline. It removes caf and reduces spark plug trouble and overheating. It can be installed by any one in five minutes. Mr. Straneky wants distributors and is willing to send a sample at own risk. Write him today.—Adv. an te er FF es =" ear

Page 103

Pu made from "i transky nple at his

POPULAR SCIENCE MONTHLY

Better Shop Methods New 10-Spindle Drilling Machine Operates Continuously HE new 10-spindle continuous rotary drilling machine illustrated was de- signed and built for drilling holes 1 in. in diameter and 1 in. deep in collar hexagon nuts used on automobile disk wheels. It is adaptable, however, for drilling other rts of a similar kind. Machinists used to an ordinary drill press will be particularly interested in this machine because of the amount of work it handles. The cold pressed hex- agon blanks for the nuts mentioned, which are 10-point steel screw stock, are turned out at the rate of 35 nuts a minute. The machine con-

The operator merely has to slip a blank into each work-holding fixture as it passes by sists of a stationary round post mounted ona base. A circular carrier supports 10 drilling spindles with their respective work tables and actuating mechanism, all of which revolve around the base. The cutting feed to the work table is obtained by a cam mechanism timed to give the operator an opportunity to load. The locating and holding of the nuts is automatic. All the operator has to do is to slide a blank nut approximately into position in each of the fixtures as it passes by. The ejecting of the nuts is automatic.

Copper Tool Used as Indicator [‘ TRUING up pulleys, shafts, studs, or other finished work in a lathe when no indicator is available, a copper tool may be used. The tool should be ground to a diamond point. Tighten the tool or tool-holder in the toolpost and run the copper point against the revolving work until it touches the high spot. Then adjust the work until it shows a copperish line of even width all around.—W. J. T.

You’ve long wanted to come to this Million Dollar School, the World’s Largest Automotive and Electrical School at Kansas City, Mo. NOW IT WILL BE EASY, because of my big reduc- tion in cost of tuition. I’ve raised the salaries of thousands of other fellows— I can do it for you, and if you decide now to come here, spend a few weeks in actual ‘“‘Learn by Doing” training, there’s a good job paying big money ready for you or a chance to go into business for yourself. But, you'll have to decide NOW to be sure of the big saving in cost of training. E. J. SWEENEY, President.

> oan "Aeasone... ‘ Auto Mechanics $50 Week and Up Learn a Good Trade One that will pay you $200 to $500 a month and more. Get in the biggest busi- ness in the world—the Automotive Busi- ness. I want to prove that you can do what thousands of men just in your posi- tion have done as a result of “SWEENEY TRAINING.” I say, take up the AUTO BUSINESS NOW. Learn it at SWEENEY'S, Kansas City, Mo. Act now while you can get the big saving in tuition. Get the Best for Less Money The SWEENEY AUTO SCHOOL offers you the greatest opportunity you ever had. A big reduction in tuition—a Million Dollar building—10 stories high—over 12 acres of floor space devoted to the “‘“Sweeney System of Practical Instruction” under expert instruc- tors. Just across the plaza from the Union Station—a short distance from the beautiful new Two Million Dollar Memorial Building. BUT, REMEMBER THERE'S ONLY ONE SWEENEY AUTO SCHOOL— THERE’S ONLY ONE SWEENEY SYS- TEM and you can only get this system at Kansas ity, Mo. You positively cannot get it any- where else.

And N Guts tthe Ol /p Start your Tuition Training AtOnca There’s Only One Sweeney School It’s at Kansas City, Mo. COME RIGHT NOW. This is the most amazing offer [ever made. If you are mechanically inclined, if you like to work with tools, you will learn under the “Sweeney System” by actually doing the work, every- thing about all kinds of automobiles, oxy-acetylene welding, vulcanizing, battery work, electrical work, building and repairing Radio sets. No experience or education needed. No books are used. You work on most complete gas engine and electrical equipment in any school in the world. Over $200,000 invested. $50,000 Radio Station WHB. You'll get dirty and greasy, but you'll learn the ‘‘Sweeney System” that fits you for the big pag jobs at $50 a week and up, waiting for Sweeney ptm men. Sweeney Systett? ‘istrucrion y oy INSTRUCTION There’s only one place where you can get this training— it’s at the world-famous Sweeney Automotive and Electrical School of Kansas City. There's only one Sweeney School—the largest in the world. There‘s only one ‘‘Sweeney System.’ No other school offers or can give you this training that not only trains you to fill big paying jobs ut saves you time and money. This training is making big moneyfor60, Sweeney Graduates. I estimate 20, 000 of them own a good paying busi- ness. Battery Experts $200 Month and Up My Free Book Tells You How to get a good mechanical job. How to Tease te be a chauffeur or truck driver. How to learn to repair any make car. How to learn to make batteries and auto tires. How to weld. How to run a garage anywhere. Shows you undreds of actual SS of men at work in my ig shops. Shows how 60,000 men got their start. Shows how easy it is to fearn several good trades; how much fun you have during recreation hours, swimming pool, entertainment, band and orchestra, radio broadcasting Station WHB. Answers every —, 64 pages beautiiully illustrated.

WRITE ME TODAY or wire me when you'll be here. Don’t wait. Come right now. Sweeney trained men in demand everywhere, $200 to $500 a month and more. You must decide now if you want to be sure of getting the big reduction in tuition. Write for my Big FREE 64-page book or wire me you are coming. No colored students accepted. E. J. SWEENEY, Pres, it’s at Kansas City, Mo.

There’s Only One Sweeney School.

our terms, methods, etc. Information. RANDOLPH & CO. Washington, D.C. Dept. 130,

NVENTORS your ‘ibeas Send for our Guide Book, HOW TO GET A PATENT, and Evidence of Invention Blank, sent Free on request. Tells Send model or sketch and description of your invention for our Instruc- tions. No Charge for the Above ' | NAME......... Ce nse tegeehe wesc enenseuene i | StreET eh wewe © cc ccccccoecececestes Se cccees ‘ i ‘ CiTy...... apace <oveccsibateteeeneanee ' "oh ca = Ee 2 ee eee Oe Bee B28 se! ee

© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

= EE SEES

Page 104

POPULAR SCIENCE MONTHLY

The New ESHMAN MASTERPIECE Complete Knockdown Set Pans

COMPLETE KNOCKDOW RESHMAN cuts: $ 92 eoenei ez “QOS THIS WO IL fe Saree ose : 3 settee Seoe NO NEUTRALIZING OR BALANCING CONDE sy i To Build the Five Tube Tuned Radio Frequency Receiver HIS WONDER knockdown set contains every single part necessary to construct the FRESHMAN MASTERPIECE. Here’s just what you get: 1 Genuine Bakelite Front Panel, pletely drilled and engraved. 1 Genuine Bakelite Sub-Panel — with sockets, binding posts and grid con- denser already in proper place. All mounting holes properly drilled. Masterpiece Tuned Radio Frequency Units—perfectly matched and bal- anced. Beautiful Genuine Bakelite Dials. Freshman Variable Grid Leak and .00025 M.F. Condenser. Freshman 5 to 1 Audio Transformer. Freshman 3 to 1 Audio Transformer. Freshman .002 Fixed Mica Condenser Freshman .006 Fixed Mica Condenser. Freshman Single Circuit Jacks. Freshman Filament Control Switch. Freshman 30-ohm Rheostat. Freshman 6-ohm Rheostat and every bracket, screw, nut, bush- ing that you will require as well as an ample supply of spaghetti and bus bar. It certainly is The Kit the Whole World’s Been Waiting. for And all $39=2° for only A 24-page book of instructions packed with every kit. Seven full-page illustra- tions and many smaller ones explain every operation step by step. Ask To See It At Your Dealer’s Look for our trademark and serial number riveted on the sub-panel. The kit is not guaranteed if number has been removed or tampered with. Chas Freshman (o.Inc. FRESHMAN BUILDING 240~248 West 40TH ST~NEW YORK,NY. © com-

w 4-inch bot pat et BD bt et et et w

| Better Shop Methods Lathe Shortcuts that Save a Machinist’s Time

By F. J. Wilhelm

"PRERE are many simple little tricks in lathe work that a machinist can use on occasion to cut down materially the time required in machining certain jobs. A few of those I have found useful in my own work are described below and they will suggest a number of others to any alert mechanic. A job too long to be finished between centers, such as turning a long shaft or cutting the thread on a long lead screw, may be handled as shown in Fig. 1. Make a bushing to fit the spindle hole in the tailstock, the inside diameter a nice run- ning fit for the shaft or screw. The first section, which will be limited by the dis- (Continued on page 131)

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GOOSE-NECK FINISHING TOOL . } ROLLS PLANE SURFACE ROLLS INTO CORNERS CUTTING EDGE Threading a long shaft, a rolling lathe tool, a punch-press attachment, and other kinks

© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. April, 1925

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Have You An INVENTION? If so the WORLD PROGRESS will show you how to Protect and Profit From Your Ideas Sample copy free. One year’s subscription 40c, Send for free “WHAT. TO INVENT” containing Suggestions to Inventors as to Inventions Needed. We invite manufacturers to address us regarding inventions they want. WORLD PROGRESS PUB. CO., INC. Room 202 Victor Bidg. Washington, D.C. ° is Beautiful Raceabout Drive Th fas RED Tnotend of Your OLD FORD | oe a Choice of Four & | Colors ; Fiat or the ae tae | , Ballet Nose Rad. 4, iator Shell. Send Ea W alog of New Aue Speed Equipment. prong en Factory. AMERICAN TOP AND BODY CO., Beech Street DELPHI. IND. $822 a Day Wnt: Write quick for new proposition. Weoffer $8.00 a day and new Dodge touring car. for demonstrating and taking orders for Comer Top = Coats and Raincoats. Spare time. No experience required. "\ : / Sample outfit free. Write now. Comer Mfg. Co., Dept. O-410, Dayton, @

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, 1935 z ) SBN) aad | 5 lp oO. April, 1925 NOTHING BUT THE TRUTH rts that the famous Polswes in- s existing patents owned by a com- — are absolutely without foundation jn the opinion of competent counsel who = minutely investigated the situation. The manufacture and sale of Polyplug will be continued—and the quality and merit of Polyplug willcontinue to keep it far in the lead of a host of inferior plugs. These features have made Polyplug the POLY PLUG Positive Permanent Contact. No screws or ‘trick’ parts. Wires quickly and easily at- tached — pulling and jarring cannot loosen contact. Instantaneous changing from head- phones to speaker. Made of genuine Bake- lite. Send for Circular H Pole Plain- 1 iyMarke POLYMET on Sleeve Manufacturing Corp. 70-74 Lafayette St., New York RADIO Storage “B” Battery 32¢e" Lasts Indefinitely—Pays for Itself performance unheard of before. Recharged Approved and listed as Standard by adio Authorities anstact Pop. Radio Laboratories, Pop. Standards, Radio ws. Lab tas, Inc. and other im- Economy and ata Grae prea b. "with Solid R: , an insur- 2. Menai heavy glass jars. Heavy Just state ber of batteries NEY 2 us rolls number of ba and we will ship aay order is received. Extra Offer: 4 bat cries in series (96 volts), $13. expressman after examining paneer i 6 per cent discount for tach at 7 Mail By o der no RLD B ATIERY COMPANY 1219 So. . Wabaah Ave., Dept. 80; Ch Chica ago, Til. Makers of the Famous World Rad Prices: 6-volt. ‘100 An i Am $12.50; 50; B20, $1 iu fo: set $16.00. World , wn RADIO RAGE BATTERIES "= Agent Users Wanted how easy it is with th — MAN KIT, which I send : rer ‘our spare time showin SELLA ER Ti os SAVING to car owners. Tals oomaier ies made, oversize, non-skid Cordis guaranteed by Bond ‘way around the world. Gan inger Plan starts you in n business all part + NO capital or experience need Ti shi Daid on approval. Lowest no Ae mt ote nes ops FREE: If you will boost MELLINGER TIRES, I have a urprising offer that will give you a set of tires | Free. Also the Master Salesman Kit with Sal wholesaie ys Be first to get my ny free pier, emazing confidene Dearest address. B. L.MELLINGER, ER, Pres, MELLINGER TIRE & RUBBER Co. Philadetph Dept. 34929, Kansas City, Mo, POPULAR SCIENCE MONTHLY Lathe Shortcuts that Save a Machinist’s Time (Continued from page 130) tance between centers, is machined with the center in place in the usual way and driven with the chuck. When this is completed, remove the tailstock spindle and insert the bushing, which is to be used as a steady rest bearing and center. Move the screw or shaft along through this bushing and through the hollow spindle of the headstock for a sufficient distance to allow another section to be turned. If a thread is being cut, have enough of the thread remain outside the bushing to start the new cut. This operation is repeated as necessary. In cutting a square or acme thread, a great deal of time may be saved by the CROSS- FEED OPERATED s~ BY HAND EQUAL TO RADIUS POINTS HELD IN PUNCH MARKS TYPE OF WORK DONE WITH FIXTURE TAPER TO FIT TAILSTOCK CUTTING ~OFF FACING TOOL TOOL Turning a spherical surface, truing a com- mutator, and using a box tool for small pins use of two todls. First, rough out the thread with a tol that is 1/32 to 1/16 in. narrower than fhe finished size of thread. Then follow yijh the finishing tool. This method avoids §ool breakage and stopping to grind theitéol, as very little stock is left for the fin%:hing tool to remove. It also speeds up the work noticeably. The tool shown in Fig. 2 leaves an ex- cellent finish when turning long shafts with a light cut and coarse feed; practi- cally no filing will be necessary. Grind the cutting edge as for regular square-nosed finishing tools. If water is allowed to drip on the point of tool while in use, the finish will be #mproved, but the work should be smeared with oil afterwards to prevent rust. Another style of tool suitable for finish- ing heavy shafts and similar jobs is shown in Fig. 3. A holder carries a hardened steel roller, which is brought to bear against the work with considerable pressure in the same manner as a knurling tool. The finish is rolled on. A good method for setting the lathe accurately for turning a taper, when it is not equipped with a taper attachment, is (Continued on page 132) © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. Radio Music Paull sade Lyri¢ ln aie HA =a l | A | il for the Critical Musicloversespe- WA cially delightin | Rauland-Lyric. | Used in all audio amplifying stages AN Hil MA | ) of aradio receiver, itreproduces with fidelity those elu- siverefinementsof tone quality which, to the trained ear, AA AAT AA mean artistic ex- cellence. Rauland-Lyric is a laboratory-grade audio transformer designed especially for music lovers. The price is nine dollars. Descrip- tive circular with am- plification curve will be mailed on request. All-American Radio Corporation, 2668 Coyne St., Chicago. IA Hil HH UN | | TRADE MARK TRANSFORMER = Choice of Noted Music Critics \E pre AME; Cay

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Bes MACHINE SHOP HANDBOOK MACHINE SHOP HANDBOOK Awonderful book for machinists, toolmakers and shop men 335 Pages—282 Illustrations HIS I. C. S. Macuine-Suop Priceonly Hanpsook is a wonderful $

bargain at $1. Contains more common sense, practical infor- mation than any other book of its kind ever published. Pocket size. 335 pages. 282 illustra- tions. A book that you will find invaluable in your daily work. Will help you get a better job and a bigger salary. Contents Useful tables, mensuration, trigonometry, proper- ties of materials, drilling, reaming, tapping and threading, lathe work, threads and thread cutting, — and testing, milling-machine work, in- dexing, helixes and spirals, key work, gearing, planer work, shaper work, slotter work, broaching, grinding and polishing and lapping, jigs and fix- tures, punch and press work, die casting, gauges, micrometers and vernier instruments, lubricants, temperature indicators, metals, heat treatment, chilled iron, welding and brazing and soldering, coating and protecting, filing, stock estimating, chipping, riveting, pipe bending, laying out work, blue prints, belting, pulleys and shafting, knots and hitches, springs and miscellaneous shop hints. Just mail this advertisement with a dollar bill and your name and address, and this 335-page I. C. S. Macuine SHop Hanpsook or any of the other I. C. S. Handbooks that you want will come to you by return mail. Money back if not satisfied.

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CLEARS

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Better Shop Methods Lathe Shortcuts that Save a Machinist’s Time (Continued from page 131)

suggested in Fig. 4. Two spots, A and B, are turned on the piece. A corresponds to the diameter of the large end of taper and should be just the right distance from the shoulder to the end of taper. B repre- sents the diameter at the small end. The angle of the taper is set parallel with the line of tool travel:-by moving the tailstock until both spots are exactly equal dis- tances from the point of the tool. This distance may be tested with an inside caliper, as shown. If the measuring is done carefully, there will be no doubt about the accuracy of the taper and very little, if any, filing will be required. Winding springs on a lathe is an awk- ward job for some mechanics. It does not need to be so if the method illus- trated in Fig. 5 is followed. The wire is passed through a short piece of brass or copper tubing and the end is gripped under one chuck jaw. Insert a tool or short steel block in the toolpost betweer the screw and the tube and press the tube down flat, just tightly enough to allow the wire to pull through without breaking. Gear the lathe for the right pitch and pro- ceed to wind the spring with the slow back gear speed. HE mandrel in Fig. 6 will find many uses in any machine-shop. It is a time-saver for turning bushings, pulleys, gears, or any cylindrical shapes within its capacity. It is especially useful for a job where the hole is over size and will not fit a standard mandrel, as well as for turning a job having a cored hole that is not to be bored out. The movable cone should be a nice sliding fit and the nut should have a right-hand thread. Figure 7 shows an effective way to drive a job on a mandrel when there is a heavy overhang that perhaps would cause the work to slip around on the mandrel, as is frequently the case when turning and facing castings with a small hole. We seldom think of a lathe doing the work of a punch press, but Fig. 8 suggests how this is possible and practical when the shop is not equipped with a press. The punch and die are constructed along conventional lines and supported in posi- tion by the saddle or by cross pieces rest- ing on the ways of the lathe. The punch holder is bolted to a top plate, which comes in contact with an eccentric shaft held on the centers and driven by a dog in the usual way. Each revolution of the spindle gives a stroke to the punch, and the speed is limited only by the ability of the operator to feed the material through the die. The punch and die are assem- bled as one unit. The fiber washer shown was a job produced by this method. As there are more ways than one to skin the proverbial cat, so there are more ways than one to produce a spherical surface on a lathe. A novel and interesting method for doing this is indicated in Fig. 9. A piece of drill rod pointed at both ends does the trick. The over-all length is equal to the radius of the circle to be (Continued on page 133) April, 1935 TRUSSES BANISHED EW SAFE WAY? Now you can throw away forever st chaf. ing leg straps and other heavy coabeseee For a well known American scientist has f

new easy way to support rupture agsist of a wonderful little invention weighing oangeus 1-25 of an ounce. Not only dod you do away with the objectionable pressure poet tight strap but you eliminate the ‘‘coming down” of ry —when running, straining, exercising, sn, etc.—which too frequently leads to Strangulation, So great has been the success of this wonder. ful device that it is being offered to ruptured H on an absolute guarantee of instant satisfacton ne free tteraturcts NEW SCIENCE INSTITUTE ee literature to 4011 Clay Street, Steubenvilie, —_ ve

Learn Cartooning At Home—in Your Spare Time from the school that has trained so many successful cartoonists of today earning from $50 to $200 and more a week. The Landon Picture Chart Method of teaching makes original drawing easy to learn. Send 6c in stamps for full information and chart totest your ability. Also state age. THE LANDON S 1451 National Bidg., Cleveland 0. DEAFNESS IS MISERY I know because I was Deaf Noises for over 30 years, My oiaites Red septic Ear Drums restored my hearing and stopped Head Noises, and will do it for you, They are Tiny Megaphones. Cannot be seen when worn. Effective when Deafness is caused by Catarrh or by Perforated, Partially or Wholly Destroyed Natural Drums. Easy to put in, easy to take out. Are ‘‘Unseen Comforts,” Inex- pensive. Write for Booklet and my sworn statement of how I recovered my hearing, A. 0. LEONARD, Suite 301, 70 5th Ave., New York OF tr ¢. Our marvellous, &

—a eye) practical MOVIE MACHINES sell.as low as $3.75 postpaid and use same size film.as big theatres, change service. M rile esd ta catal PARAMOUNT MFG, CO. Dept. PS7 Boston, Mass. ClearYe:! Me. Your Skin Can Be Quickly Cleared of Pimples, Blackheads, Acne Eruptions on fe face or beriy. Barbeau Itch, Eczema, Enlarged Pores and Oily or Shiny Skin, Write today for my FREE BOOKLET, FREE **A CLEAR-TONE Sa et, i cured myself after being afflicted 15 years. E.S.GIVENS, 153 Chemical Bidg., Kansas City, Mo,

ARITHMETIC oF ELECTRICITY A practical treatise on electrical calculations of all kinds reduced to a series of rules, all of the simplest forms, and involving only ordinary arithmetic. 200 pp, Price, $1.50. POPULAR SCIENCE MONTHLY 250 Fourth Avenue :: NEW YORK SELL BY MAIL Mail Order Men, send for our Dollar Making Circular Service. Circulars with your imprint fare nished at one-fourth original cost. Make 92 cts. profit on each dollar order. Add our service to your regular line and watch profits grow. PARTICULARS FREE!

© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

D. L. ELFCO, 525 S. Dearborn, Chicago

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g ESPEGSEEESS = yp OO gcilieFi | “SOME | Fe zs a ee fiFEE i April, 1925 This Book FREE 144 es and valuable to those who want de- pendable household, automobile and shop re- ‘pairs with big savings. Smooth-On No. 1 On your car, stops leaks in radiator, bursted water jackets, tank, hose con- nections and at gaskets without taking down. Keeps bolts, nuts, grease cups and hub caps from dropping off. In your home, stops leaks in water, and steam pipes, tanks and pots, roofs, etc. In the shop, makes any kind of pres- sure joints, joins wood, metal, glass and concrete to each other and holds on any metal--iron, brass, lead, aluminum. Makes handles, screws and nuts last- ingly tight. Be your own “‘fixer’’ and save much money for better things. To get perfect results, write to us for and use the Smooth-On Repair Book. Free if you mention this magazine. Get Smooth-On No. 1 in 6-02., 1 lb. or 5 lb. tins at any hardware store. SMOOTH-ON MFG. CO. Dept. 58 574 Communipaw Ave., Jersey City, N.J. Ask your Radio Dealer to show you these KELLOGG PARTS: Audio Frequency Transformers New-Type Low-Loss Variable Condensers Radio Frequency Transformers Write today for free 5-tube radio frequency circuit diagram IS) KELLOGG Kellogg Switchboard & Supply Co. Chicago, Lllinois g =e Vand up Selling concentrated, non-alcoholic f ood SES Fe Gutranteed und: ae 3 food lowe. All lavecs. Selle insvery hice. sed every day. Not sold in stores. = femal Bie repeater. 100 per L—1—-F 0) ME, ATE 3 Pi a = Re ag H 55 iit if 78 # oath nak & steady income. Write quick, American Products Co. 1177 American Bidg., Cincinnati, Onio an Saw Books FREE a > “Saws in the Shop,’’ ‘Saw Sense,’”’ ‘‘Saws on the Farm.”’ Just send us your name and address and say which of these helpful books you want and we will send it FREE. Write NOW, E. C. ATKINS & CO., Inc. Dept. D-20 Indianapolis, Ind. Af i : Z for Machinists, Car- penters and Tool Makers; none better; thirty styles. Quarter. ed oak and metal cov- ered. Ask for booklet. **Built for Service’’ The Pilliod Lumber Co., Swanton, Ohio POPULAR SCIENCE MONTHLY Tool Cases: Better Shop Methods Lathe Shortcuts that Save a Machinist’s Time (Continued from page 132) turned. A center punch mark is made on the side of the cross compound and a similar mark is put on the tailstock in the center and in the same plane as the one on the compound. The circle first is roughed out as closely as possible to a templet. The points of the rod are placed in the punch marks and the carriage held hard against the rod. By using a round nose or any suit- able tool, the job then may be finished to a true circle. Engage the cross feed and hold the carriage against the rod while the tool is cutting. Either concave or convex surfaces may be produced by this method. For a con- cave surface hold the rod against the tail- stock. For convex surfaces put the rod On the opposite side and hold it against the headstock. Have you ever tried to true up a com- mutator and bring the mica down smooth with the surface with a hacksaw blade or other means? A much better and quicker way is by planing it off with the lathe carriage. Grind a tool such as a cutting- off tool from 1/16 to \ in. wide. Give the tool one-quarter turn in the holder, with the cutting edge toward the shoul- der, and plane the mica in each groove down smooth by working the carriage back and forth by hand (Fig. 10). Figure 11 illustrates the use of a box tool in the engine lathe. A tool of this type may be rigged up for many small manufacturing jobs, such as_ turning, facing, and cutting off small pins, small bushings and similar jobs. Many varia- tions of this tool are possible and with different size guide bushings, many sizes of stock may be handled. Cheaply Made Follow-Rest HE follow-rest illustrated is an aid in turning shafts of small diameter, especially when other equipment is not available. This simple arrangement will do the work as well as a more expensive special follow-rest. A wooden block is cut and drilled to receive a machine bolt. The top piece, iii) HARD sel = 42>. — ar AE ee O— == SAS CROSSSLIDE OF LATHE A follow-rest made mainly of wood which bears against the shaft, is of hard wood and is mounted on the block with wood screws. The follow-rest is bolted to the carriage with a machine bolt, which passes down into a plate under the ways of the cross slide. When necessary, the bearer can be adjusted for height with packing pieces.—CHARLES KUGLER. Strong and Be Light ESE aluminum levels have unusual strength. The lenses are made of a non-brittle glass that withstands rough usage. You can use a Sand’s for over- head work and at arm’s length without fatigue. Plumb Right Window frames and doors are plumb when you use a Sand’s. So are walls and foundations. Sand’s accuracy is built-in by factory experts. : Sealed Tight The spirit tubes are set and sealed immovably. Sand’s accuracy is permanent. The protecting lenses form a double-seal that is dust- proof and moisture proof. The Choice of Master Craftsmen Sand’s is the “buy” word for levels with careful workmen everywhere. Sand’s Levels have made good on the job for thirty years. At Good Hardware Stores Everywhere SANDS LEVEL & TOOL CO. © © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. 5849 Fischer Ave., Detroit, Mich,

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AVE you a good typewriter in both your home and H office? 1f not, you are running the risk of costly errors, misunderstandings and criticism—no matter how well you write. All business and personal letters and invoices should be typewritten. It is the method used by modern men and women, old and young, and any- one can afford a machine on our plan. We will send you one of these wonderful typewriters with no obligation to you whatsoever. Send no money. Just fill out and mail the coupon, This brings full particulars of our Free Trial Plan made by special arrangement with the express com- =. Take ee of our Remarkable New Special Price Offer which makes it so easy for you to own this handsome full size machine with all late style fea tures and modern operating conveniences. 10 Days Free Trial! We want you to give this wonderful typewriter b: in the most thorough test in your own home or office. You cannot imagine the perfection of this beautiful machine antil you have seen it and used it. You send no money. When the typewriter arrives, you deposit only $3 with = express agent. Test it thoroughly for ten days. Then if you are not satisfied it is the greatest bargain—the very finest typewriter E fra have ever seen, just return it to your express agent and he will promptly return your $3 to you. If you decide to keep it; you make monthly payments so small you will never miss them—just like rent—and then this wonderful writer is yours. No “‘ tape’’—no annoyance—no d Five-year written guarantee with every machine. e . A Lifetime Bargain! We are giving you the lowest price ever made on this wonderful machine—late style models—up- to-date—just like new— absolutely highest quality rebuilt, perfect ad- ustment and fully guaranteed. The world famous BALL- BEARING L. C. Smith has set the standard of quality and long service for over 20 years. It is the easiest running and longest wearing type- writer ever built. The choice of “oe and discriminating users all over the world. Over half a miilion sold. No ma- chine leaves our factory unless it is 100% perfect in every tail. Our prices are so low because we are the world’s t exclusive dealers in L. C. Smith Typewriters. You cannot buy a typewriter at anywhere near our price that will give you as many years of satisfactory service. Free to You Now! A Complete Course of Lessons on touch typewriting; Tools; and Waterproof Cover; Complete Operating instructions; all given with your machine. This is the easiest typewriter to operate and learn. Anyone can use it. Send the coupon now before this offer is withdrawn. SMITH TYPEWRITER SALES CORP., 321-360 E. Grand Ave., Chicago FREE TRIAL COUPON POPULAR SCIENCE MONTHLY

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Simple Fixture Aids in Bending Bar Stock Quickly HE bending fixture shown below was made for shaping a few special parts as cheaply as possible. In the same way many similar jobs may be handled at a minimum expense. A flat cast-iron plate is planed on one side only. The form is turned to the cor- rect radius and fastened to this plate with three fillister-head screws. Two strips of 14 by 1 in. cold-rolled steel are fastened to the plate adjacent to the form and with a The bar-bend- OF i; ; ing fixture

sage )

space between equal to the width of the stock that is to be bent—in this case 14 in. The bending lever, which is a piece of Vs by 1 in. cold-rolled steel, swings on a stud passing through the center of the form. It is provided with a steel roll 2 in. in diameter, set to roll the work up close to the form. The lever stud has no nut on top, so that the lever can be removed for inserting and removing the work. The work is heated at the point where the bend starts, and the sharp angular bend is made by holding it in the vise. The steel is put between the holding strips on the fixture, the bending lever is put on its stud, and the bend made.—H. L. W. Cutting Odd-Sized Core Boxes on a Circular Saw HE most difficult part of building a core box is in making the circular cut for the core. This often is done with a saw having a corresponding radius, but if the radius of the saw available differs from that of the cut to be made, the problem becomes more complicated, es- pecially if there are no other tools at hand with which to do the work.

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contains 900 mechanical movements; 40 per petual motions. Tells how to obtain and sell patents. Suggests new ideas. Explains how to select your attorney and avoid patent sharks. Special price (for a limited time) $1.00 post paid. Albert E. Dieterich, 681-A Ouray Building,

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IS} This seal on a radio or tool advertisernent signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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POPULAR SCIENCE MONTHLY TEN’ TRADE MARKS:COPY:?IGHT PROTECT YOUR INW ANY NEW article, machine, design or improvement there4 bination of parts or improvements in any known article whicif increases its efficiency or usefulness, may be patented, if it involves inventif® if You Have Any New Meas which you feel are useful, practical and novel, take prompt action to protect your rights. If you have invented any new machine or new combination of parts or improvement, or any new design or process, SEND DRAWING, MODEL OR DESCRIPTION of it for information as to procedure to secure protection. DRAFTING and SPECIFICATION ROOM of CLARENCE A. O’BRIEN, Registered Patent Lawyer, Washington, D. C. All communications are held in strict confidence. My personal, careful and thorough attention is given to each case. I offer you efficient, reliable and prompt service—based upon practical experience. Highest references. NO CHARGE FOR ABOVE INFORMATION Write today for free books, ‘‘How to Obtain a Patent’’ and ‘Inven- tion and Industry”’ and blank form ‘‘Record of Invention.”’ These books will give you valuable information, and they may.save you much time and effort. Send for them now. My practice is devoted exclusively to United States and Foreign Patents and Trade Marks. Write me freely, frankly and with full paca ing it is very probable that I can help you. These Books Free Use the Coupon attached, and immediately upon its receipt I shall send you the form Record of Invention to be returned to me with drawing, description or model of your idea; promptly upon re- ceiving your idea I shall write you as to procedure and costs. CLARENCE A. O’BRIEN REGISTERED PATENT LAWYER Member of Bar of Court of Appeals, District of Columbia, United States Court of Claims; Supreme Court of United States, Supreme Court District of Columbia. s------------- FREE COU PON ---------------- CLARENCE A. O’BRIEN, REGISTERED PATENT LAWYER 8891 Security Savings and Commercial Bank Building Directly across Street from U.S. Patent Office, Washington, D. C. Please send me your free books, ‘‘How to Obtain a Patent” and ‘‘Invention and Industry” and blank form, *“‘Record of Invention,’’ without any obligation on my part. L fier 2) rics |. UT ma — e and in| = $ }_—~ IMPORTANT—WRITE OR PRINT NAME CLEARLY. © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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POPULAR SCIENCE MONTHLY

“I’m Going to Make More Money!” “I’m tired working for a small sal- ary. I know I have just as good a head on me as Fred Moore and Bob Roberts, for we used to work side by side. But they’ve gone far ahead of me. “Why? Because they saw the value of special training, and I didn’t. “But I know better now. If the International Correspondence Schools can raise the salaries of men like Fred Moore and Bob Roberts, they can raise mine, too! “If they have helped others to ad- vance, they can help me. To-day—right now—I’m going to send in this coupon and at least find out what the I. C. S. can do for me.” INTERNATIONAL CORRESPONDENCE SCHOOLS _ Box 7647-D, Scranton, Penna. Without cost or obligation on my pat. please tell me how I can qualify for the position or the subject before which I have marked an X: BUSINESS TRAINING COURSES

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] GC ZZZZZZZZZA One end of the shaft runs the thread- ing die on; the other turns it off pressed into the die as shown. When the desired length has been threaded, the rod or bolt is drawn from the shaft, taking with it the die-holder. This, of course, stops the die-holder from rotating. The shaft never stops. To run the die off the bolt, it is placed on the left-hand end of the shaft, as shown at A, the rod or bolt being held with the pliers as before. * With a little practice threads may be eut rapidly and, accurately. The cost of the machine is small, in this case being only $1.50 for material and a few hours’ work.—H. E. B.

Constructing Swivel Vise Jaws to Hold Tapered Work Erm A . {WIDTH OF VISE liye PIN~ PRESS FIT” TO SUIT IN JAW VISE JAW p oR i pe 7m ~ CUT! OUT ad

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ae e . S ib : » To the Man With an Idea I offer a most comprehensive, ex- perienced, efficient service for his prompt, legal protection and the development of his proposition. Send sketch, or model and description, © for advice as to cost, search through* prior United States patents, etc. Pre- liminary advice gladly furnished with- out charge. My experience and familiarity with various arts, frequently enable me to accurately advise clients as to prob- able patentability before they go to any expense, , Booklet of valuable information and form for properly disclosing your idea, free on request. Write today. RICHARD B. OWEN Patent Lawyer 6 Owen Building, Washington,D.C, 41-D, Park Row New York City

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on = ee) e- h- th to b- to d by New York O Suite 1007 Woolworth Bldg. Philadelph ia, Pa., Office Suite 714-715 Liberty Bldg. POPULAR SCIENCE MONTHLY OUR OFFER: Your first step YY Before disclosing an invention the inventor should write for our blank form “RECORD OF INVENTION.” ‘This should be signed, witnessed and returned to us, together with model or sketch and description of the in- vention for INSTRUCTIONS. NO CHARGE FOR THE ABOVE INFORMATION Our Four Books Mailed Free to Inventors Our Illustrated Guide Book HOW TO OBTAIN A PATENT Full instructions regarding U. S. Patents. Our Methods, Terms, and 100 Mechanical Movements illustrated and described. OUR TRADE MARK BOOK Shows value and necessity of Trade Mark Protection. Information regarding Tvrade Marks and unfair competition in trade. OUR FOREIGN BOOK We have Direct Agencies in Foreign Countries, and secure Foreign Patents in shortest time and at lowest cost. Progress of Invention Description of World’s Most Pressing Problems by Leading Scientists and Inventors ALL COMMUNICATIONS AND DATA STRICTLY CONFIDENTIAL INTERFERENCE AND INFRINGEMENT SUITS PROSECUTED Private Office, Victor J. Evans, with View of Patent Office Through Window Fea or niet seetegtrecrrsiateaiersweetrsi tm ighest References Prompt Attention Reasonable Terms I VICTOR J. EVANS & CO., Patent Attorneys | i | Main Offices: 760-9th Street, N. W,, Washington, D, C, | Gentlemen: “Please send me FREE OF CHARGE your FREE books as described above. | i COUPON | Name............ lai ale hala ee alae 0s haar eae . PamamieMnORe MS tM WOE ie Oe. Pe Dag Wl aD. Ral odirn ectiew os Sale sings RON | © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. Chicago, Ill., Office Suite 1114 Tacoma Bldg. er a Py Pittsburgh, Pa., Offic Suite 514, Empire Bldg. % 24 nats | San Francisco, Cal., Office Suite 1010 Hobart Bldg.

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683 WOOLWORTH BUILDING New York City 411 TOWER BUILDING Chicago, Ill. 522 SCIENTIFIC AMERICAN BLDG. Washington, D. 364 HOBART BUILDING San Francisco, Cal. 219 VAN NUYS BUILDING Los Angeles, Cal. “heb ge a Books and Information on Patents and Trade Marks By Request. Associates in All Foreign Countries. POPULAR SCIENCE MONTHLY PATENTS TRADE-MARKS DESIGNS FOREIGN PATENTS MUNN & CO. PATENT ATTORNEYS ‘Associated since 1846 with the Scientific American C. Bossert- Built Houses Can Be Erected By 2 Persons Within Few Days Time From Homes to Summer Bungalows We Have the Type You Want. No Delay or Waste in Erection! There is a Bossert House for every need. Whether it is a substantially constructed home for all-year use, or a cozy little bungalow for your summer weeks at the seashore or in the mountains, Bossert has the type that exactly meets with your requirements. Every Bossert Sectional House is built at our plant by experienced and highly skilled builders. The house is delivered to you either sectional or ready-cut as desired, complete with plans and_ specifications; millwork; plasterboard (when specified); hardware; paint and varnish. Architect’s fees, builder’s wastes, and construction delays are eliminated. Be- cause you deal directly with one of the oldest and largest lumber plants in the East you are guaranteed highest quality and complete satis- faction with lowest prices. We have a handsomely illustrated cata- logue of Bossert houses which we will be glad to send you free upon receipt of your address. Write us TODAY. Consult Bossert first for: Homes, Summer Bungalows, Club Houses, Garages, Church Buildings, Hospitals and Additions. Louis Bossert & Sons, Inc. Largest Lumber Plant in the East (House Dept.) 1310 Grand Street BROOKLYN, N. Y. DISTANT STATIONS | | WITH THE C APE ger volume, finer selectivity, less in- terference. Lasts forever. The one big advance yet made in tuning. Ratio 12 to 1. - Quickly applied to any shaft. For sale by all good Radio Dealers. If unableto obtainfrom dealer, enclos $2.00 for Royal Brass Finish. ¢ $2.50 for ff Satin 4 yA t § i | Silver Ly Finish. H | $3.50 for fj DeLuxe § Gold F Greater range, big- | | Plated H >» Finish. Hy aw ¢ i LS @ 1410 W.59thStreet D VERNER DIAL > ) The Apex Super Five is a tuned radio frequency receiver of the highest type Built into a highly finished wainut cabinet — complete withJones Multiple Battery Cable—all settings highly gold plated. List price {4 $95.00 complete. ept.403 Chicago April, 193 | They shorten greatly the period | each disease. | | _ apply to cases of blood poisoning number of mixed strains. | ‘THE bacteria used to produce thes | America. | the various strains or types are selected | and cultured. | immunology was the discovery that sus | ceptibility lies between the ages of one | and two, when only 30 per cent of children | are immune. | than are country children. | reason, young men from the crowded | tenements during the war stood up | against disease ravages where men from IS] This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. xf == The Magic Stuff that Saved Nome (Continued from page 29) convert them into vaccines of the order. These are used where ve quick immunizing response is need . . . . Te i for preventive immunization. “— Bacterins and serobacterins ap e€ m mostly from several strains ~ of e When a person nen monia, for example, it may be onet this infection out of several possible types: or it may have been caused by a number of mixed strains. The same thing might The infections are commonly mixed, Therefore it is vital, at times, that Serums contain antibodies effective against a products come from typical cases in hospital and private practice all ove The specimens are examine by bacteriologists for identification, and One of the important developments of ceptibility to various diseases—diphtherig among them—could be told by skin tests made by injecting preparations of disease germs between the layers of the skin: In this way the presence or absence of suff- cient natural specific antibodies in the blood could be determined through slight inflammation or lack of it, at the point of inoculation. Thus experiments were begun to learn why a few children never contracted diphtheria, although exposed. The rea- son was found in the antibodies in their blood. This led to the Schick test, by which the immune children could be picked out. It led also to the develop ment of the toxin-antitoxin immuniza- tion, which makes susceptible children safe from diphtheria. phar gna see by the way, is pecu liarly a disease of children. Very young infants usually are immune, it being believed that antitoxin from their mothers’ blood passes into their bodies before birth. The highest degree of sus After the age of three the number of children contracting the dix ease falls off rapidly. Why, though, should some children be immune and others not? The answer 8 that repeated exposures to disease, coupled with the strength to throw it off, gradually build up immunity. For this reason city children, constantly exposed to slight infections, are less a prey t0 diphtheria and similar infectious diseases For this homes in sparsely settled sections went down easily. For this reason, too, aa isolated community such as Nome 1s @ particular danger from epidemics diphtheria, and the danger is heightened (Continued on page 139) Apeit, 1 becau skill Th antit¢ the | separ the h ducec that ' tion | be ct with poun Th bulky is cor easily the st A” perha dren’ brous disco Henr work Th scarle throu strair After strate could as in It demo by ct tococ cause Sey from A034 later Ag: that fever. muni posut schoo home to se: New susce Th not ¢ but { ment minis those T I cocel orga) eases las, foun ing ¢ neut prov Serui (blo

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these 8S in | over mined ny and lected nts of at sus. itherig n tests lisease in. In f suffi- in the slight dint of » learn racted ie Tea- . their st, by Id be velop- uniza- ildren pecu- Very ne, it . their bodies of sus- of one ‘ildren ee the e dis- ren be wer is isease, it off, or this <posed rey to iseases r this owded od up n from ; went 00, al e is in ics of htened

——

Apeit, 1925 POPULAR SCIENCE MONTHLY

— o The Magic Stuff that Saved Nome (Continued from page 138) cause medical supplies and medical skill are likely to be lacking. The latest development with diphtheria antitoxin is in a super-concentrated form, the result of years _of experiment to separate the antitoxin substance from the horse-blood serum in which it is pro- duced. This was the sort of antitoxin that was carried into Nome—an explana- tion of the fact that 300,000 units could be compressed into a package, which, with its wrappings, weighed only 20 pounds. ae ; The modern antitoxin not only is less pulky than the serum of former years, but is correspondingly more potent and more easily and quickly administered, without the suffering once forced on the patient. mona outstanding recent develop- ments is the fact that scarlet fever, perhaps the most troublesome of chil- dren’s diseases, at last seems to have been brought to control and prevention by the discoveries of Drs. George and Gladys Henry Dick, of Chicago, and of former workers. The Dicks wroduced experimental scarlet’ fever in human_ volunteers through the use of cultures of various strains isolated from scarlet fever cases. After producing this disease, they demon- strated that susceptibility to scarlet fever could be determined by skin inoculation, as in diphtheria. It is believed, though not positively demonstrated, that scarlet fever is caused by certain specific strains of the strep- tococcus, the deadly bacterium that causes blood poison of different types. Seventy-four per cent of the deaths from scarlet fever occur in children under 10, and survivors frequently develop later trouble due directly to this malady. Again, as in diphtheria, it is probable that the natural immunity from scarlet fever, acquired by many, is a contact im- munity, brought about by repeated ex- posures and mild infections. In a private school, with students from protected homes, 85 per cent were found susceptible to scarlet fever, while in a public school in New York City only 22 per cent were susceptible. The means now are readily available not only for carrying out the Dick test, but for applying the immunizing treat- ment to those susceptible, and for ad- ministering the scarletinal antitoxin to those manifesting symptoms. THE germ of scarlet fever is thought to be only one strain of the strepto- coccus bacterium. Other strains of this organism are responsible for serious dis- eases, including blood poisoning, erysipe- las, and childbirth fever. Science has found a way to produce a serum contain- ing antibodies capable of antagonizing or neutralizing a wide variety of these ns, and recent advances have im- Serum. Experiments with antistreptococcus (blood poison) serum in smallpox cases

(Continued on page 140)

Proved the activity or potency of this | | | |

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© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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POPULAR SCIENCE MONTHLY

between acts HEN he’s not amusing folks on the stage of The Follies, Will Rogers has other ways of turning minutes into money. With his Corona, in his dressing room, he turned out his famous book, “‘The Illiterate Digest’’ — the best selling book of humor of the year. * ” . * That’s the advantage of owning a Corona. You can use it any- where, any time—make some- thing of the spare moments most people squander. By the way, have you seen the New Corona Four? It has a full- size standard keyboard, the same as big office machines, yet it is portable. Corona Four costs only $60. Easy terms if desired. Look for Corona in your phone book or write Corona Typewriter Co., Inc., 112 Main St., Groton, N. Y.

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True-Tone ! Saxophone Easiest of all instruments to play, and.one of the most autiful. Three first lessons sent free give you a quick easy start—in a few weeks you can be playing popular tunes, No teacher neces- sary. You ean take your P placeinaband ororchestra fin ninety days, if you so desire. Most popular instrument for dance orchestras; home entertainments, church, lodge and school. A Saxo- ™ phone player is always popular socially and has many opportunities to earn money. Six Days’ Trial and eacy payments arranged. (105) Shows all = Free Saxophone Book 30075" taodels and gives first lesson chart; also pictures of famous orofessi and orchestras. Just send your name for a copy. Director Bennie Krueger and His Orchestra. Bruns- wick Records. The Magic Stuff that Saved Nome (Continued from page 139) are reported to have shortened the course of the disease and prevented pitting and secondary infections. In erysipelas, strep- toecoccus pneumonia, streptococcus com- plications in scarlet fever, and in other in- fections, this serum has brought marked advances in medicine. This serum also has been experimented with in the treatment of pernicious anemia. One theory regarding this little understood disease attributes it to auto- intoxication of intestinal origin. Autointoxication, or deterioration of the powers of the blood through the ab- sorption of poisonous matter not properly eliminated, is one of the commonest of ail- ments that make life miserable and ultimately kill. Wrong diets or sedentary habits cause bacteria to infest the intes- tines, and the toxic substances that result give rise to ailments that are hard to fathom. Medical research in this direc- tion has produced artificially the acid- ophilus bacillus, which in normal health flourishes in the intestinal tracts and de- stroys enemy bacteria. ‘lait kien is a peril that we all face. This disease, claiming one-tenth of all who die from infancy to old age, may never be conquered altogether, but extraordinary work has been done in its subjugation. Some years ago a pneu- monia serum was produced from the blood of horses inoculated with pneumonia bacteria. This serum, though successful, contained protein matter from the horses’ blood that caused harmful reactions in the patient. Also, lacking hospital facili- ties, the ordinary practitioner was unable to use it. Recently, however, Dr. Frank W: Huntoon succeeded in taking the antibod- ies out of the serum entirely and suspend- ing them in a clear water solution. This pneumonia antibody has been used with considerable success and has sufficed to cut down somewhat the reactions that ordinarily followed use of the horse serum. There are mixed serobacterins, too, useful in preventing or treating common colds and bronchitis. Next to pneumonia and tuberculosis, typhoid fever is the most deadly of dis- eases, attacking fully half a million per- sons in the United States every year, of whom every seventh person dies. eed in the armies of the world typhoid has been wiped out by the discovery of immunization, and it would disappear from civilian life if inoculation were to be practised universally. The average dura- tion of immunity is 30 months. Occa- sionally one injection of typho-bacterin prevents an attack of typhoid fever. The immunization is harmless to healthy per- sons, and confers almost absolute immu- nity. I should mention, too, the development of a vaccine against hydrophobia, the marvelous work of the lockjaw antitoxin, which has eliminated this disease from the armies of the world as a cause of death,

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STANDARD RADIO CO., 104 East 13th, Kansas City, Me

April, 19 ‘Why alread gracef maxin — rio! < Als of 17-i to ext largest was 62 great | reason to rec of ligh gases, wheth in mu

Page 115

, 1925 —_ City, Me. April, 1925 eg ———— ee a oe Fy Why the Eclipse Was Late (Continued from page 39) it is beginning to change from the oi, symmetrical form it holds at the maximum sunspot period to the shorter, prighter form that marks the minimum 7 a photographs made with a camera of 17-inch focal length showed the corona to extend 2,000,000 miles into space. Our largest camera, the focal length of which was 62.5 feet, did not show this amazingly t extension of the corona rays for the reason that its lens was not fast enough to record the exceedingly rapid passage of light through this enormous distance. “ ITH the large camera, however, we obtained images of the moon 714 inches in diameter, which is on a scale large enough to work out the details of the structure of the corona. This is the prin- cipal topic of inquiry at all eclipses, of course, for the corona—the fiery halo of the sun—is seen only at such times. “Photographs made with cameras of yarious focal lengths will enable us to determine the laws of distribution of the materials making up the corona. “We used also two interferometers to determine the distribution of the gases in the corona and also the motion of the gases, our chief hope being to determine whether the corona rotates with the sun in much the same way as our atmosphere retates with the earth. } “We employed a small spectroscope ‘to find out the relative brightness of the various gases in the corona, and two large - | spectroscopes in an endeavor to determine ‘what is the distribution of the metallic ‘vapors immediately above the sun. “Investigations of this sort are of prime interest to the astronomer; of little inter- est, though, to the layman, to whom an eclipse simply is a splendid spectacle. The spectacular features of an eclipse escape the scientific observer almost en- tirely. That has been my experience, at any rate. ed AT THE recent eclipse, for example, the amount of spare time I had during thetwo minutes of totality was exactly 15 seconds. During the rest of the time I was exposing photographic plates, or making ready for the next exposure. Some day, though, I may get an opportunity really to see an eclipse. “As in other expeditions, we set up a camera also to determine accurately the photographic diameter of the moon as a check on the Einstein theory. We know the distance of the moon from the earth, and we are able to compute its diameter. Photographs obtained with this instru- ment, which has a focal length of 15 feet, may enable us to ascertain whether the otographic diameter of the moon checks th its computed diameter. Many sci- entists believe it will not; that the photo- ‘gtaphic diameter is larger. If they are right, it will show that some force other than that assumed by the Einstein theory is the cause of the deflection of the light of the stars that are nearly on the same e as the sun. ; “That the eclipse was late.in. arriving (Continued on page 142) POPULAR SCIENCE MONTHLY ‘Ideal’ Grinder didit all.” FRED MILKERT, Roselle, iil. writes: “Last June I sharp- ened 256 lawnmowers for which I received $542.00,” 00 Da neasd INONE 2° Earned mont: ANew Business—Big Business A Business to Enthuse Over — The “Ideal” Lawn Mower Sharpener A wonderful invention that ahergene fawn mowers scientifi- cally—quickly—perfectly; does t FRED C. MILKERT OF ROSELLE, ILL., WRITES: “The Ideal Lawn Mower Sharpener put § me in business, starting in the basement of my home and forcing me now for the third time to move into bigger quarters. Today the dream of my life— a shop of my own — is realized. With amachine like yoursanda little hustle any man can havea business of his own and beindependent. D. H. NOAKES, MILFORD, OHIO, WRITES:‘‘Several years agoI started sharpening mowers inaldx 10 shed. Today I own a store of my own on Main Ave., No. 212, valued at $8,000.00. The W.F. KENDT, BUFFALO,writes: ZENO BRANDON, MIDDLE- Isharpened 994 lawnmowers last _— suntet —— a y Yaene th eipts were nearly .70 in ays wi a $2100.00 which is not bad Have made as high as $38.70 in one for a side line.” day.” No town toosmall. You Start Now Lawn mowers are dull—owners don’t know where to get them sharp- 4 ened. Mowing the lawn dreaded i yj or improperly sharpened mower. Lawn mowing *® healthful, invigorating and pleasant when Mower is ‘‘Ideally’’ sharpened. You do the work scienti- fically—you are in big demand. Lawn Mowers Sharpened to Razor Edge=— People glad—owners delight in mowing lawn with mower sharpened on an‘‘Ideal.’’ Mower runs light—click-click-click and the grass is cut. Build permanent business for yourself.Start now! a TODAY jaan catalog and booklet High and ‘‘Let George Say It.’’ Write today. The Fate-Root-Heath Co. High and Bell Sts., Plymouth work as nothing else can. ecause of dull — Detailed The Fate-Root-Hea Bell Sts. Please mail at once free Illustrated y Catalogand booklet‘*‘LetGeorge Saylt.’ y PUGS. «cS ivdidencsccenues caccnveauphunain Address o © ‘aucohsiceetea seen aa A TEST EVERY MAN PAST 40 SHOULD MAKE Medical authorities agree that 65% of all men past middle age (many much younger) are afflicted with a disorder of the prostate gland. Aches in feet, legs and back, frequent nightly risings, sciatic pains, are ; some of the signs—and now, a member of the Am- | erican Association for the Advancement of Science lias. written a remarkably interesting Free Book that tells of other symptoms and just what they mean. No longer should a man approaching or past the prime of life be content to regard* these pains and conditions as inevitable signs of approach- ing age. Already more than 20,000 men have used the amazing method described in this book to restore their youthful health and vigor—and to restore the prostate gland to its proper functioning. Send im- mediately for this book. If you will mail-your re- quest to the Electro Thermal Company, 4044 Main Street, Steubenville, Ohio—the concern that is dis- tributing this book for the author—it will be sent to you absolutely free, without obligation. Simply send name and address. But don’t delay, for the edition of this book is limited. Western Office, Dept. 40J, 711 Van Nuys Bldg., Los Angeles, Calif. AMBASSADOR Low Loss Products Master Tuning Coil Perfectly Balanced Head Phone w Loss Condenser High grade, standard radio prod- ucts that will increase the effi- ciency of any set and add to the satisfaction of the user. Ambassador Low Loss Products have long been. the choice of particular fans. See them— compare them, and you will choose them too. At all good dealers ‘ Write for FREE circuit diagrams in which Ambassador products can be used. AMBASSADOR SALES COMPANY G 108 Greenwich St., New York 326 W. Madison St., Chicago Why BOSTON? Because it has exclusive features ALL Rubber Oblong Button, holds stockings taut—for trim ankles, Hook and Eye Cast-off—for - convenience. Slide Adjustment—for fit and comfort. No metal parts on face of pad —no wrinkles. The pad without a pucker. GEORGE FROST COMPANY, Makers, BOSTON HOW DID YOUR GARTERS ? © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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e~ a 95 an Hour! “Every hour I spent on my I. C. S. Course has been worth $95 to me! My position, my $5000 a year income, my home, my family’s happiness—I owe ‘it all. to my spare-time training with the Interna- tional Correspondence Schools!” Every mail brings, letters: from some of the thousands of I. C, S. students tell- ing .of promotions or increases in salary as the rewards of spare-time study. What are you. doing with'the hours after supper? Can you afford to let them slip. by un- improved when you can easily make them mean s0 much? One hour 2 day spent with the I. C. S. will prepare you for the position you want in the work you like best, Yes, it will! Put it upto us to prove it. Mail the Coupon for Free Booklet INTERNATIONAL CORRESPONDENCE SCHOOLS — Box 7646-D, Scranten, Penna. Without cost or obligation, please send me one of your booklets and tell me how I can qualify for the position or in the subject before which I have marked an X: BUSINESS TRAINING COURSES - Business Management Salesmanship Industrial Management Advertising Personnel Organization Better Letters Traffic Management Show Card Lettering Business Law Stenography and Typing Banking and Banking Law Accountancy (including C.P.A.) Nicholson Cost Accounting Business English 1 Service Railway Mail Clerk Q EI Bookkeeping Cemmon School Subjects Private Secretar: High School Subjects Spanish O French Llustrating TECHNICAL AND INDUSTRIAL COURSES Electrical Engineering Architect Electric Lighting Architects’ Blue Prints Mechanical Engineer Mechanical Draftsman Machine Shop Practice Ratliroad Positions Engine Operating ‘Civil Engineer Surveying and Mapping Metallurgy 0 Mining Steam Engine*ring (j Radio Contractor and Builder Architectural Draftsman Concrete Builder Structural Engineer Chemistry 0) Pharmacy Automobile Work Airplane Engines Agriculture and Poultry Mathematics Street 3-6-24 Address...... State International Correspondence Schools Canadian, Limited, onzrcal, Canada “LIBERTY” ELECTRIC each SOLDERING IRON — Guaranteed For One Year © lquipped with Finest Quality . - Ifeating Element. Has Separable Plug, Six Foot Cord and*Removable Copper Tip. Handy for Home, Radio and Electric Jobs.’ 110-120 Volts, AC or DC Russell B. Créssman, 200 Fifth Ave.,N. Y. City, Dept. “S” DeForest License © HONEYCOMB COILS The Universal all-wave inductance. Back and front panel mountings. Send 25c for_ Super Het., R. F. and Honey- comb Coil Circuits and Complete Catalog. ‘ Chas. A. Branston, Inc. t. 9 Dept. 9, 815 Main St. Buffalo, N. Y. | fore cannot compute with entire accuracy | the width and length of the shadow. | moon is influenced not only by the gravi- | cannot determine. “many persons saw on the snow. | seems to be offered by the fact that, while | the shadow bands were clearly observed | | wings of airplanes. POPULAR SCIENCE MONTHLY Why the Eclipse Was Late (Continued from page 141) at the various stations occasioned con- siderable comment. There is nothing extraordinary, however, in this. In the five eclipses that I have observed, some were late, others early. The reason for this is that we do not know the orbit of the moon with extreme accuracy, and there- ““T hie size of the shadow depends on the relative distances between the sun, the | moon; and the earth. The orbit of the tational attraction of the earth and the sun, but by several other planets, and just | how much this deflects it in its orbit we If the shadow of the moon is slightly smaller than is computed, the eclipse will be late, as was the case with the recent one. If it is slightly larger, it will be early. An unavoidable error of only part of a mile will cause the eclipse to arrive either late or early. When we consider with what vast distances astronomical calculations are concerned, an error of part of a mile is not particu- | larly great. s HIS latest eclipse may bring us some- what closer to solving the mystery of shadow bands—those amazing and elusive plays of light and shadow that We | attempted to photograph them with a high-speed motion-picture camera in order to determine accurately their direction and velocity, but they eluded our camera. “IT understand, though, that moving pictures of the shadow bands were made successfully at the Wesleyan University observatory, Middletown, Conn. “Since the eclipse several possible expla- | nations of the shadow bands have been offered, some quite tenable, including the conventional. explanation that they are due to heat motion in the air. “Some substantiation for this theory on the ground, they were not seen on the The speed with which the airplaries were moving, though, rather | than the low temperatures in which they | moved, may have been the cause of this. NV ITH the radio tests our expedition | was not actively concerned. The | results of these tests, so far as I have been | able to learn, seemed more or less incon- clusive. In some places radio reception was reported to have improved during the darkness of totality; in other places lis- teners reported no difference. “‘Photographs of the eclipse made from | the air were for the most part of scant value to science for the reason that the rapid motion of the planes caused dis- tortion in the pictures. Perfect definition would have necessitated that the plane be at rest, absolutely immovable, at the time each photograph was taken. Pos- sibly a method of bringing this condition about may be developed in the future. | | Also, improved photographic apparatus some day may make it possible to photo- | graph the moon’s shadow from the air and | thus fix its path with absolute accuracy.” © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25 8 Fels, Mink, Catch Fish eitiiespioie gd — repre geivenine’ STEEL catches them like a fly t t i FREE TRAP OFFER, Bargain Cateie rie Witite for our & Formula on best: Bait known for catching all 1s clin ‘WALTON SUPPLY CO. Dep.14‘St.Louis, Me ~ ——— Unusual tunity is oe Mr. Brush Salesman for ager tling me Oren ; ms ambitious Ceeive ling men to represent an old established manufact we high grade, guaranteed, fastest selling line f Saver of Iwisted in Wire Brushes, sold direct to the i Sani have openings for experienced brush men ag ‘nee in all territories. We want live wire, energeti Getters. We pay larger commissions than Eciic: Ge. Brush House in the Country. If you want to en, other real money, it will pay to write us immediatel our proposition. WIRE GRIP SANITARY BRUSY CORP., 15 Mercer Street, New York City. Fishing facts and hints. Tells how to compete in ; our annual $2,000 Fish- Photo contest. A postal ae ' gets it FREE! i “oll ag SOUTH BEND BAIT COMPANY t 14579 High Street South Bend, Ind. ¢ | Squab Book FREE Squabs selling at highest prices ever known, Greatest market for 20 years. Make money breeding them. Raised in one month, We ship everywhere our famous breeding stock “\ and supplies. Established 24 years Write now for big illustrated free : How to Make Money Breeding Squabs, PLYMOUTH ROCK SQUAB CO, "616 Hi St., Melrose Highlands, Mas, \ “ Protect your tools from theft. Write any ed sheer any design on tools and metal with electricity like writing on paper with en or pencil. Complete outfit $3.50, prepaid anywhere. Interest- ing descriptive circulars free, Write to-day. Agents wanted. Arkograf Pen Co., 1171-A East Stark St.,Portiand, Oregon our facto routing C) ~ Easily sold. Over one million sat- isfied wearers. No capital orexperience required. Largesteady income, Manyearm $100. to $150. weekly. Territory now being allotted. Write For Free Samples, MADISON SHIRT M'F'RS, 505 Broadway, New York BUCHSTEIN’S FIBRE LIMB is soothing to your stump~ strong, cool, neat, light. Easy payments, Guaranteed 5S Years Send for Catalog Today P. BUCHSTEIN CO., 610-3rd Ave., So. Minneapolis, Mim. LASS AS¢ PING BUY DIRECT FROM THE MAKER CATALOG FREE Either pin shown made with any 3 letters and 2 / figures. 1 or 2 cofors enamel, Silver plate 25/ \ ea. $2.50 doz. Sterling silver. 40¢ ea.. $4.00 doz. B 4 BASTIAN BROS. CO. 650 591 Bastian Bidg., Rochester, N. Y. seis Agents ape 2000500 Instant weld new scientific princi ple. Without heat or cement quickly repairs punctures or blow outs. Money back guarantee. Get wise te this new seller, every auto owner a pros: pect. Exclusive territory. Write for FREE sample and full details. TOURIST PRIDE MANUFACTURING CO. Desk 45C MINNEAPOLIS, MINN. high € factul cheap natur: has as speci2 sweet selves comp “ In the el as the poun¢ vestig ness travel lower taxes the t excav of the suspe of thi: “ 2a der ir ine, ¥ lose. produ cottor natur cellul the re ‘O now tutes autor ‘| that resea

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© What a whale of a difference Just a few cents make WAY cess POWERFUL TELESCTP® a”, Ba

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3 eeag aset sowacsee® ee S POPULAR SCIENCE MONTHLY seaman \eaeseenesen: peeaaaseuses q factory. Be certain! formance. table mounting. At dealers everywhere. \e DON’T GAMBLE in building your set by using inferior parts. You chance the loss of considerable time, money, and patience if the results aren’t satis- Use only Amsco parts. really know their business, they lead the field in all around per- Amsco Parts necessary for those who construct their own include the Low Loss Condenser, a laboratory instrument designed for perfection in set building. Also the Amsco Rheostat, for perfect filament control with all types of tubes and the Amsco Tube Socket with genuine Bakelite Base suitable for pane! or aMSDP Made by men who Free literature on request AMSCO PRODUCTS, Inc., Broome and Lafayette Sts., New York © Oe a owen " machine gu nteed A-1 condition. ilt by experts. SOLD ON INSTALLMENTS ju greguleg £500 a a he | wn. undreds of well-known o> on x wv pl presee, for FREE list ae models and bargain prices ms - Do it Now. ag RELIABLE ADDI 368 W. Washington Street our of - 104 CHICAGO, ILL. You Can Play a Hohner Harmonica! This FREE PC non Instruction Book Will Teach You How Millions of happy people of all ages are now playing Hohner Harmoni- cas for entertain- ment, education and popularity. Anyone can quickly learn to play a Hohner with the aid of the Free Instruction Book. This interesting and instructive book contains a series of easy lessons, charts and pictures which will enable you to quickly master the harmonica and play operatic, classical and jazz selections. Even though you have had no previous musical training, you can learn to play a Ilohner Harmonica. And when you do learn, you will have mastered the first principles of a musical education. Don’t hum or whistle—play it on a Hohner. Ask your dealer for the Free Book today. If he can’t supply you, write to M. Hohner, Inc., Dept. 182, New York City. . Leading dealers everywhere sell ‘Hohner Harmonicas—50¢ up. are GOOD Casez Machinists, Toolmakers and other particular mechanics appreciate their splendid quali- ties. Catalog free. Write for it to-day. H. GERSTNER & SONS 516 Columbia St.. Dayton, 0. AGENTS «oon mxcomr Youcan sell Premier Knife Sharpeners to housewives, restaurants, stores, etc. 9 out of 10 will buy. Selis for 50c. Writetoday for attractive LARGE offer. PREMIER MFG. CO, PROFIT Dept. 9 Detroit, Mich. for you You Save 50% World 6-Volt Storage Batteries 7 are famous for their guaranteed | Approvedand quality and service. Backed by Listed as years of Successful Manufacture Standard by and Thousands of Satisfied Users. Leadin You save 60% and geta Authe rity BS 2-Year Guarantee Bond | ;,...uding Radio In Wri News Labor- World Battery owners ‘“‘tell their friends.’” That’s our best proof of performance. Send your order in today. atories, Popular Science Insti- tute of Stand- ards, Popular RADIO BATTE: Radio Labor- Seni... Bi a % eres . « e. - Volt, 140-Amperes * 5° 16.00 er ae -_ 6-Volt, 11-Plate .... $12.25 | Lefax, Inc. yct oe reg a bE 4 -Volt, 7-Plate ....« .00 Ss olid Rubber SEND NO MONEY Container Just state battery wanted and we will ship day order is received, Now Standard by Express C. O. D., subject to War ment on all your examination on arrival. orld Storage Extra r: 6% discount for | Batteries. me cash in full with order. Buy now | ™ore leakage or and get a guaranteed battery at breakage o — 50% saving to you. A or rotting of box. WORLD BATTERY COMPANY 1219S. Wabash Ave., Dept. 7 Chicago, Ill. April, ing - GERSTNER CASES| | —~_—$—__ Here Are Correct Answers 4), Questions on Page 7; | 1. A little over 27,000 gallo for-each acre of land. One inch Ps Water New York City means that about #2 and a half billion gallons of water f ne the land covered by the city. pha 2. Deafness sometimes is due trouble with the nerves of hearer al a the little water-filled sac in which th nerves end, but merely to some ear oh struction that prevents the sound vibra tions from reaching this sac. In cases of this kind sound vibrations that enter ¢h teeth may be conducted to the easaae| through the bones of the head and ray be heard in this way. y 3. Nowadays the commonest materiak |’ for phonograph records are those belong | ing to a class of manufactured substances sometimes called “artificial resins.” ‘The artificial — are made by chemical processes, mainly out of produc distillation of coal. “ “—" 4. A little air dissolves in water, just as salt or sugar does. When a glass of water stands around _ : while, some of this air comes out of solution and mak little bubbles. ae 5. A few fishes eat seaweeds or other | fishes,. but most fishes live on the miero- scopic plants and ‘animals, millions of which are contained in every cubic inch of the surface water of the sea. 6. The full moon is always visible in the daytime when it is above the horizon and not hidden by clouds. Daylight simply makes it less noticeable. | 7. They really evaporate just as water | does out of an open pan. The chemical | from which moth balls are made is one of | the substances that can evaporate directly | from the solid state without having to| pass through a liquid one. 8. Yes, any electric motor can interfere | with radio in its neighborhood if the motor | -is improperly adjusted, so that sparks are | produced at its commutator. This causes | a clicking in near-by radio sets as the| motor turns. It usually can be stopped! by overhauling the motor. 9. Probably, but not for a very long time. | There is no friction in empty space, as there would be if the earth were revolving in air. The only known thing that is tending to stop the earth is the friction of | the tides in the ocean. Probably this) really does slow up the earth a very little, | but the slowing is so small that science | so far has not been able to detect it. 10. Because of the powerful magnets in the dynamo. The little hair-spring of your watch is made of steel. Under the| influence of the magnets this spring) sometimes gets magnetized. After that | it attracts the other steel parts of the| watch and will not work properly. | 11. It is the unit in which scientists | measure the strength of light. Originally, it was the strength of the light given out by a standard candle made of a certail kind of wax and of a certain fixed size A light one candlepower strong 1s just | about visible a mile away on a cleat, | dark night. | 12. Yawning is a stretching and relief of | the muscles of the chest and of the breathing apparatus, usually after these muscles have been tense for some time. } _ - ae sible it seé insta trans cuss inter piece bewé look two end tion to d mig] of tk broa If Pp as b not | you you you in ¢ you wall you a fe mor! of li can illus hav but the slen by 1 ast¢ you the the hei adv 1g pris loo! ove sur the let

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Pril, 193 ee TS to 71 ft Water rain jn Ut five ; to or with h these Car Ob. 1 vibra. Cases of iter the Car-sa¢ nd May aterials |" belong. stances “pet The hemical 3 of the Just as of water of this kes the ions of ie inch 2 in the zon and simply S water hemical 8 one of directly ving to nterfere € motor rks are 3 Causes as the stopped ig time, aCe, as volving that is ction of | ly this | y little, | science | it. mets in | ring of der the spring er that of the ientists iginally ven out certain od. size. is just . clear, lief of of the r these ime. i ————— ————— Do Your Eyes Lie? (Continued from page 38) sible to change the ugly thing and make it seem quite beautiful. i To go back to the house proposition, for instance. You have seen how easy it is to transform an exterior. Suppose we dis- cuss a few things we might do with the interior of a house. If the builder has placed your mantel- piece too high, you don’t have to sit and bewail your fate at having all your rooms look ill-proportioned. You simply place two long, tall vases on the floor, at each end of your mantelpiece. Your imagina- tion draws the connecting lines that seem to draw down the mantelpiece. Or you might place two low, fat vases on the ends of the mantelpiece itself, and one of those proad, fat clocks in the middle. F YOUR whole room is too high, try placing objects with vivid colors, such as bowls of bright flowers, on the tables; not on the mantelpiece. By such methods you can direct the eyes where you will; you can keep them down if you like. Or perhaps your room is toolow. Then you would run parallel stripes, rather pale in color, from the floor to the ceiling, or you would place a long mirror high on the wall, to reflect the ceiling, and so make your room look lofty. Mirrors always give a feeling of space. Nowhere is the principle of color har- mony—and, for that matter, the principle of line—mere important than in dress. I can give you one very simple instance that illustrates them both. Just recently we have discovered that a row of white glass buttons straight down a black dress, from the throat to the hem, can give a look of slenderness. You can suggest a line just by three or four buttons. Or, you will be astonished to find how slim you can make yourself look by wearing dresses cut with the lines sloping inward a little toward the top. That adds an inch or so to your height, too. Then there are the ‘‘ distinctive,” as the advertisers would say, sleeves and cuffs. If you have short fingers, you’ll be sur- prised to discover how much longer they look when you wear a cuff that droops over the hand. And you’ll be equally surprised to discover how much shorter they look than they really are if you wear anumber of rings or if you wear a brace- let close to your hand. HEN there are shoes. If you have normal sized feet, you never have to worry about them. If you haven’t, there are all sorts of things that will help you make them look normal. A short vamp, for instance, makes the foot look shorter. With a long vamp, the reverse is true. Laced shoes make the ankle look smaller, just as button shoes make the ‘instep look higher. The black patches on the fancy white sport shoes that run back from the toe along each side, make the whole shoe look smaller by luring the eye away from the true outline. If you can take an ugly outline and superimpose a beautiful outline, you de- ceive the eye into seeing only the beauty and being oblivious of the ugly. And that is the esthetic value of optics. POPULAR SCIENCE MONTHLY gy Wer Crs SE THERMIODYNE ULTRADXRE MURDOCK Azarkh MICHIGAN — Deresnadyne MALONE LEMON MASTER RADIO HARMONY AUDIOLA « GLOBE EAGLE ANnp ‘MANY OTHERS USE ‘FHORDARSONS ! FOLLOW THEIR LEAD Super Het Builders! For the “‘Best’’ 45,000 Cycle Super- Heterodyne, ‘‘RADIO”’ and other leading publications recommend in highest terms the Thordarson 2:1 ratio transformers. Take no others! name. 6- THORDARSON Tollow All stores can now supply Thordarsons. substitutes. 145 the Lead he Leaders! Build or replace with Thordarsons Leading set builders have scientific laboratory appa- ratus to test, compare and prove the facts about trans- formers. They continue to use more Thordarsons than all competitive makes combined! Doesn’t this answer the amplification question? Unconditionally Guaranteed HORDARSON AMPLIFYIN Standard on the majority of quality sets They Say (Continued from last month) THEY SAY OF THE ANDREWS DERESNADYNE: “It secures the finest tone and high selectivity with increased volume and distance. comparable to the original. anything from a mute tone to a volume that fills a large hall.” It brings to the home reproduction of music really In volume the Deresnadyne will give Deresnadyne amplifies with Thordarsonst THEY SAY OF THE RADIODYNE: “When you own a Radiodyne you can hear singers’ voices and orchestral harmonies faithfully reproduced through the loud speaker. . so clear and distinct that you lose nothing.” Radiodyne amplifies with Thordarsons! 1 No need to accept If dealer is sold out, order from us and mention hie TYPES AND PRICES; Thordarson ‘‘Super” Audio Freque Turner are now to be had in three ratios: 2-1, $5. 3-1, ry 4 Thordarson Power Amplifying Transformers are $13 the pair. Thordarson Interstage Power Amplifying Transformes, $8. Write for latest hook-up bulletins—free! FACTURING CO. AGENTS 500% PROFIT GENUINE GOLD LEAF LETTERS Guaranteed to never tarnish. Anyone can put them on stores and office windows. Enormous demand, large profits, Paul Clark says: smallest day $28.70. R.L. Reel made $920 in two months. Write today for free sample and liberal offer to general agents. DRAW CARTOONS TURN YOUR TALENT INTO MONEY Cartoonists earn from $50 to $300 per week —some even more. Our new Circle System of Drawing quickly trains you to become a cartoonist. Send in stamps for booklet and sample lesson plate explaining full details of course. THE NATIONAL SCHOOL OF CARTOONING 415 Park Building Cleveland, Ohie Se JUST 17c im a Day Pays for this Beautiful Chair Over 1000 other bargains. Furniture, Rugs, Lamps, Silver, China, Blankets, Stoves, etc. Save Big Money at our Factory-to-Family prices. Pay as little as $3 down; up to a year and a half to pay balance. Get all your Furnishings at once—pay as you use. Thou- ands buying this new way. Big Catalog FREE New Spring ‘‘Larkin Book of Better Homes.” Shows everything for parlor, porch, dining-room, bedroom, kitchen. Bargain Prices on famous Sympho- nola Phonographs. Also Symphonic Pianos, Player- Pianos in genuine Mahogany, Walnut, Fumed Oak. Free trial. Up to 4 years to pay. Satisfaction or money buck. heck below article interested in. CF Home Furnishings C) Pianos or Players () Phonographs (Cut out this adv.—write TO-DAY for FREE Book. Litkite CO tz. Dept..440, BUFFALO, N. Y. Peoria, Ill. Chicago, Ill. © This seal on.a radio or toel advertisement ‘signifies the approval of the INSTITUTE OF STANDARDS. See page 25. Caille 5-Speed Motor in a Light Weight Twin Raising and lowering steering handle changes pitch of propeller blades giving variable speeds forward, reverse and neutralin addition tospark and throttle control. (See cut below.) Motor has twin cylinders—no vibration. Light weight. Rope starter. Send for our free book on Rowe boat Motors. THE CAILLE PERFECTION MOTOR CO. 6340 2nd Boulevard Detroit, Michigan oO 2 Speeds Forward—Neutral—2 Speeds Reverse a Note Change in Pitch of Blades

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\ Condenser! POPULAR SCIENCE MONTHLY 2 tee message came from one pleased radio fan—from just one radio fan—but the experience of many others is identical. And you, too, will find that a Dubilier By- Pass Condenser in your set will eliminate noises—purify reception—and do the work magnificently! - Dubilier CONDENSER AND RADIO CORPORATION ‘Old Town Canoes” Days that merit fond reflection Days when the lake is crystal clear and the sky is cloudless overhead—these are such days as vacation dreams are made of. Get an “Old Town.” Here is a sturdy canoe of unusual beauty. “Old Towns” are low in price. $64up. From dealer or factory. vy v v The 1925 catalog shows all models in snappy colors. It is free. Write for your copy today. O:tp Town Canoe Co., 1594 Main St., Old Town, Maine, U.S.A. EADING profession- als, like Carroll Mar- tin, famous trombonist of Isham Jones’ Orches- tra choose Conn instru- ments because of Conn supremacy in tone, tune, mechanism and easy playe ing qualities. You’ll get ahead faster with a Conn, socially or professionally —win new friends, make big money if you choose. ‘Carroll Martin Cultivate Your “Musical Bump Conn is the only maker of every instrument for band: saxophones, trombones, cornets, etc. Write now for Free Book‘‘Success in Music and How to Win It,”” by Sousa and other artists,and details of Free Trial offer. Mentioninstrument. C.G.Conn,Ltd., 432 ConnBldg.,Elkhart,Ind. ; ; IN] IN a ‘ \ “4 BA STRUMENTS IN Wonss LARoEST Lentutshchiitetaeed IS} This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. n (Continued on page 147) Your Colds (Continued from page 41) the membranes of the nose and throat too dry, which is harmful. Warm, dry air makes us very susceptible to colds The humidity never should be allowed to drop below 40 per cent and should be above 50 per cent for the mogt healthful conditions. How you may determine the humidity of a room by means of a hygrometer, or dry-and-wet. bulb thermometer, is shown in the chart on page 41. If the relative humidity is below 50 per cent, water should be evaporated in the room. If the home is heated with a hot- air furnace, there is a place provided ip the furnace for water. This should be kept full. If it does not supply enough moisture, pans of water may be placed on or below the registers. If the home is heated with steam or hot water, pans of |;*” water may be placed on the radiators, or containers for water may be placed behind the radiators. 7° THE factor of humidity as a cause for greater susceptibility to colds in congested centers must be added the ease of travel for germs that thrive in the heart of a crowded city. Every streetcar and subway train, every place of assem- bly, is a favorite stamping ground for the germs of disease. Moving-picture thea- ters and other indoor amusement estab- lishments enable them to thrive, multiply, and spread their baleful influence. In the country, on the other hand, these agencies of distribution are lacking, and so the rural population is relatively less sus ceptible to colds. For similar reasons, indoor workers are likely to suffer more than tnose whose occupations keep them in the open air. The exception to this rule is found in the case of the outdoor worker who is sub- jected to severe exposure. The weaken- ing effects of exposure render him espe- cially susceptible to the graver menace of pneumonia. Another factor of impor- tance is the question of home conditions of the outdoor worker. If he spends his nights in close, ill-ventilated, and con- gested surroundings, the comparative im- munity from minor disorders will be nullified. In the prevention of colds medical au- thorities say that there are two important factors: IRST, the common cold, at least some varieties, is extremely contagious. Prevention lies in avoiding contact with sufferers; for the colds may be trans- mitted through the common drinking- cups, roller towels, door-knobs, hand- shaking, sneezing, or coughing. Second, colds are most apt to attack overfed, under-exercised and constipated people, and those who avoid fresh air. To avoid colds, therefore, keep fit; avoid overeating, eat fruit and fresh vegetables and not too much meat or pastry; get outdoor exercise daily. To keep the tone of the body high, and therefore less sus- ceptible to colds, avoid too heavy, soggy flannel underwear or, on the other hand, underwear of weight so light that it allows a chilling of the skin at every — | wintl | their js no of th | mort | stim | train lack man, after How early by a atels vent (pre! brisk by 4 shor prev | the « | quer is no | lead The shou of tl

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» 1925 en- > of or- ons on- im- au- ant me US. ith ns- ng- nd-

Your Colds (Continued from page 146) : zephyr. Individuals differ in ee nieanuts in this respect, and it is not wise to lay down any rule. A quick cold-water sponge, especially of the throat and chest, upon rising in the morning, followed by a brisk rub, will stimulate the circulation in the skin and ‘train it to a quick response. Wet feet, lack of sleep, and over-fatigue bring on many a cold, and should be avoided. The treatment of the common cold after it appears, never is very satisfactory. However, if the cold is detected at a very early stage, you may avoid some misery by a hot full-tub bath, followed immedi- ately by rest in bed in a fairly well brisk purge such as may be accomplished by a dose of magnesium sulphate. These measures may be helpful in shortening the course of the malady and in preventing involvement of the ear and the cavities of the head, which not infre- | quently occurs, and remember that a cold is not a simple matter. Neglected, it may | Jead the way to a really serious disease. 'The services of the family physician

_ should always be sought in severe attacks of this much neglected malady.

How Quickly Can You Stop Your Car? (Continued from page 81) eases each driver had his foot on the accelerator and was forced to shift posi- tion. The smallest elapsed time in these instances was 35/100 second. With most of the subjects the time lost was from four- to six-tenths of a second. With hand brakes the average was even higher. Applied to various rates of speed, the bureau measurements show astonishing results as to the distances traveled in the half-second interval of mental reaction established as the average. Ata speed of 15 miles an hour the progress of the car during this interval is 11 feet; at 20 miles, | 13 feet; at 25 miles, 18 feet; at 30 miles, | 22 feet, and at 40 miles about 28 feet. ; The workings of a driver’s mind are influenced by many factors. He may | have the habit of considering problems | | unconnected with the immediate job of piloting his car, and may become so deeply absorbed that emergencies do not register | quickly on his mind. Some psychologists believe drivers may be hypnotized by | such factors as glaring headlights. These

ventilated room for 24 hours or more | (preferably three days), light diet, and a

observers maintain that the brilliant | beams induce hypnotic sleep in the driver |who is tensed with watching the road ahead; also that many motorists lose mental control in the sharp glare of con- centrated lights from an approaching car. But whatever may be the cause of mental slack in any individual case, Uncle Sam’s scientists believe their mea- surements will be of practical value in awakening drivers to greater alertness and caution, and in setting new standards of driving efficiency. Further, they believe that present brake-testing methods may be revolutionized by apparatus that more closely duplicates emergency conditions.

‘SEND NO MONEY.

|

POPULAR SCIENCE MONTHLY

147 Scientists and experimenters choose Eveready Columbias

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EVEREADY COLUMBIA Dry Batteries -they last longer Popular uses include— gas engine ignition telephone and telegrat doorbells — buzzers motor boat ignition heat regulators tractor ignition starting Fords ringing burgla: pe eon . protecting bank } vaults . ; \ electric clocks . calling Puiman t cy porters . firing blasts lighting tents and ening Se running toys radio “*A”

longer. Manufactured and guaranteed by NATIONAL CARBON COMPANY, New York Canadian National Carbon Co.. Limited, Toronto, Ontario

FOR home or factory electrical experimental work, Eveready Columbia Dry Batteries are supreme. give experimenters power of known and dependable quality. Famous scientific and industrial laboratories everywhere use them for delicate work in preference to other sources of electricity. When not in use they rest quietly, renewing their strength for further experiments or tasks of utility and convenience. For every dry battery use, select Eveready Columbia Dry Batteries—they last

They Fahnestock spring clip bind- ing posts on the ignitor at no ex- tra cost to you. Ask for them by name at electrical hardware radio automobile marine supply implement and general stores Eaten San Francisco

2 Genuine Diamonds 4/100 Each Cut Stones, No Chips Solid Gold Terms if desired (6 mos. to Pay ) 14 kt. White Gold Top. Gold Emblem (any Lodge) or any Initial (Old English) Inlaid in Genuine Poy oN HOPE RUBY Que > Oe Also, in Black Onyx No. 6132 Send size of finger Thig .Reg. Trade Mark iNl t , red for inunection. © "* guarantees you equine diamonds. Send for Free Catabg DFCcCMSwW Ay Letter

Buffalo J Mfg. Co., “The Mail Order House” agg! gi Oe soa Buffalo, N. Y Dept. A © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

WORK or pleasure may bring suffering — even tor- ture. But a few. drops of Absorbine, Jr. quickly brings relief and makes feet fit for another day. $1.25 a botile at your druggist’s W.F. YOUNG, Inc., Springfield, Mass.

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IE LEY EPP RPL FE GE OH POPULAR SCIENCE MONTHLY Balkite Battery Charger. Charges 6 volt “A” storage batteries. Price $19.50 West of Rockies $20 In Canada $27.50 An unfailing Balkite “‘B”’—re- places “‘B” batter- ies and dry cells. Operates from light socket. Price $55 . Ins Canada $73 power supply for both circuits Hereat last is an unfailing power sup- ply for your radio set. Balkite Radio Power Units furnish constant uni- form voltage to both “A” and “B” cir- cuits and give your set greater clarity, power and distance. The Balkite Bat- tery Charger keeps your “A” storage battery charged. Balkite “B” replaces “B” batteries entirely and furnishes plate current from the light socket. Both are based on the same principle, are entirely noiseless, and are guaran- teed to give satisfaction. Sold by lead- ing radio dealers everywhere. Radio Ty alkite Power Units BALKITE BATTERY CHARGER — BALKITE “B” PLATE CURRENT SUPPLY Manufactured by FANSTEEL PRODUCTS CO., Inc., North Chicago, Illinois April, 1925 ‘Installed the Miraco myself and I ave never had any experience with radioatall. Have gotten Havana,Cuba, and Honolulu,’’ reports H. Kittle. haw, Miss. ‘*Miraco is a wizard. I have handled radios for two years— have not seen its equal under $200. Heard Havana, Cuba, Saturday night despite that their language is hard to discern on a radio.’’—C,G. Stockman, Snyder. Neb. ‘*My Miraco works fine. Nov. 28th, I got 5NO, Newcastle, England, and LP, Berlin, Germany. Can you beat that record?’’—Thomas Walker, Howell, Mich. COAST TO COAST RECEPTION veritied by Miraco users Pennsylvania Hears Calif. Miraeco works fine. Last Have listened toCuba, Cal- night I got Cuba on loud ifornia and possibly 100 8 e. otherstations. Allwhohear t pr i Miraco proclaim it the best localinterference.—Clinton they have ever heard.—G. Elliott, Long Beach, Calif. H. Stevens, Altoona, Pa. Reports like these from users in every state prove Miraco Tuned Radio Frequency sets—at rock-bottom ices—have efficiency of sets costing 3 times as much. Made by pioneer set buiiders. Factory-built, completely assembled, factory-tested, and guaranteed. Easy for beginners to cperate. 5 tube set $75. Order direct from this ad or MAIL COUPON BELOW for special offer, latest bulletins urther testimony and proof that Radio offers no finer, moderately priced receiv- MIDWEST RADIO CORPORATION '408 - Y E 8th St., Cincinnati, Ohio i Send free literature, SPECIAL OFFER and full particulers. O USER QAGENT QO DEALER § RPO e eee eee ewer eee eeeseserese A New Socket that means Better Reception! After exhaustive research our engineers have developed Viralon, a special glass, processed for 100% efficiency. Sturdy and rugged, absolutely heat and moisture proof, and unaffected by those influences that make many other socket materials inefficient as insulation. Other exclusive features are Ezyklean Contacts (proof against corrosion) — One- Piece Contact Strips—Handy Soldering Ter- mijarals, etc. Price $1.25, standard size. Write for interesting pamphlet If your dealer cannot supply you, send us $1.25 and parcel post to cover each socket. DURAY RADIO CORPORATION Dept. 17, 263 Washington Ave., Newark, N. J. OURAY ALL-GLASS VIRALON eo SOCK To Select a Loudspeaker (Continued from page 78) usually is made in such a way that the motion of the armature is magnified at the diaphragm. All diaphragms have a natural vibra- tion period of their own, and this has to be taken into account in the design of the loudspeaker. Otherwise there will be a tendency to greatly emphasize the tones in human speech or the musical selection that most nearly’corresponds to the vibra- tion period of the diaphragm. The size and shape of the horn has a lot to do with perfect reproduction and there are a thousand and one other diffi. culties to keep the manufacturer of loud- speakers awake nights figuring out ways to overcome them. GREAT many radio fans build their own loudspeakers out of old phono- graph horns, or homemade horns, and a single head phone or loudspeaker unit. Often these outfits give excellent results, especially when they are not forced to reproduce loud signals. The homemade loudspeaker that combines great volume with fine tonal qualities is rare indeed, and if you must have both volume and quality, it is best to buy the factory- built loudspeaker. The most progressive radio dealers today are fitting up soundproof booths in their stores where they demonstrate re- ceivers and loudspeakers. Always be sure to have the dealer show you what the loudspeaker will do on both loud and weak signals and with various stages of amplification. Even if your ear is not musically trained, you can tell when voices sound natural and lifelike. In lis- tening to orchestral selections, see if you ean distinguish between the various in- struments. If the voices sound high and tinny, it is because the loudspeaker is failing to repro- duce the low notes. Deep, hard-to-under- stand voices indicate the loss of the high notes and overtones that make human speech clear to the human ear. Since head phones give such excellent quality, it is worth while to ask the dealer to allow you to listen on a pair of them plugged into the detector stage of the re- ceiver. By listening with a pair of head phones and the loudspeaker alternately, you will be able to judge the quality of the loudspeaker. T IS not fair to condemn a loudspeaker offhand because one or two selections do not reproduce clearly. The broadcast- ing station itself may be to blame, for some of them occasionally send out radio waves that are far from perfect reprodiic- tions of the sounds produced in the studio. over the time schedules“ of the various stations, you should arrange your visit to his store at a time when you know that, one of the better local stations is to be on the air with a good program. F YOU are a beginner in radio, you won’t want to miss an article next month telling how to build a single- tube receiving set of unusually simple construction, yet of high efficiency. In justice to the dealer who has no control |, et © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. degt in 8 mak addi cou} easil pote shou ing | a first rheo to t Nov stat ing rear min men the post con! to t Thi wire ove est ‘tha fror the Cor the

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» 1925 T the the bra- S to the ea ones tion bra- aS a and liffi- yud- ays heir n0o- id a init. ilts, l to ade ume and ory- ers is in Te- sure the and s of not hen lis- you _in- it is pro- der- high man lent aler hem > Te- 1ead ely, the aker ions ast- , for adio dio. trol ‘ious it to that, e on - April, 1925 How to Build a Radio- Frequency Amplifier (Continued from page 75) degrees with the panel L. A slight error in setting the angle of the coils will not make much difference, however, since the additional feed-back when the coils couple together can be compensated for easily by a small change in the setting of potentiometer J. The sockets J and K should be placed with the filament bind- ing posts away from the panel L. The filament circuit should be wired first. Connect one terminal on each rheostat and run a branch from this wire to the negative-A-battery binding post 3. Now connect the other terminal of rheo- stat G with the right-hand filament bind- ing post of socket J (as seen from the rear). Next, connect the remaining ter- minal of rheostat H to the left-hand fila- ment terminal of socket K (as seen from the rear). The two remaining filament binding posts on sockets J and K now can be connected and a branch run from this wire to the positive A-battery binding post 4. This completes the filament wiring. tens outside terminals of potentiometer I should be connected as shown in Figs. 1 and 3. One terminal goes to the wire between the rheostats and the other over to the wire from binding post 4. Run a wire from the end of coil B near- est the panel over to the end of cecil D ‘that also is nearest the panel. A branch from this wire should be connected with the center terminal of potentiometer J. Connect the plate terminal of socket J with one terminal of coil C and connect the other terminal of this same coil with the plus-B binding post 5. Now connect a wire between the rotary-plate terminals of variable condensers E and F, as shown in Fig. 1, and from this wire run a branch to the wire going to the center terminal of potentiometer J. Next, connect the stationary-plate terminal of condenser E with the grid terminal of socket J and from this wire run a branch to the remaining terminal of coil B. These connections are shown clearly in Fig. 6. Now connect the sta- tionary-plate terminal of condenser F, the grid terminal of socket K and the remaining end of coil D in the same fashion. AFTER this, connect the plate ter- minal of socket K with binding post 6 and connect the two ends of coil A with binding posts 1 and 2, as shown in Figs. land 2. This completes the wiring of the radio-frequency-amplifier unit. The order in which the connections have been described results in making all the hard- to-get-at connections first. The final step is to connect the radio- frequency amplifier with your receiver. All ordinary regenerative receivers, regardless of the types of instruments used in them, operate on the same general Principle. First there is a coil connected with the antenna and ground. This is called the “primary circuit” and may consist of a few turns of wire placed close to the secondary coil, or of many turns (Continued on page 150) POPULAR SCIENCE MONTHLY 149 It Charges —any size —all make The Tungar is a G-E product, developed inthe great Research Labora- toriesofGeneral Electric, The New Model Tungar charges Radio A and B batteries, and auto bat- teries. Two ampere size (East of the Rockies) $18.00 The Tungarisalso avail- able in five ampere size, design unchanged (East ofthe Rockies) $28.00 60 cycles—110 volts ALO NET en OE ~ - m8 ort eect The new Tungar will keep your storage batteries up—fully charged all the time. It charges radio “A” batteries of 2, 4, or 6 volts. Radio “B” bat- teries of 24 to 96 volts. And auto batteries, too. It makes no disturbing noise — is simple —charges while you sleep. Just clip the Tungar to the battery, plug it in on the house current and leave it overnight to charge. A Tungar at home means clearer tone—full volume—your set at its very best all the time for all that’s on the air. PAT, OFF. Tungar—a registered trademark—is found only IS) on the genuine. Look for it on the name plate. Merchandise Department General Electric Company, Bridgeport, Conn. GENERAL ELECTRIC Buy Direct _fromFactory Combination Get manufacturer’s prices. Ranges Save 1-4 to 1-2 on stoves ranges, furnaces, and mec | $§Q80 household oods during the ' —— - Up f hour shipments.30 == monthly, Money-back guarantee. 24- / ys’ crial in your eS cus- Va CoV CeViiCey sly) voce Direct to You” © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. c Pe DIVIDES reatest sale in our25years NEW Dees of $100 Machine. istory. Cash or easy pays meee uabee 3 all Times. ments—terms as low as ; —SEND NO MONEY TRIAL OFFE Guaranteed for Life Anyone can operate it. Will not make mistakes. Let this machine do your figuring, First cost is last cost. Do away with pencil stubs and scratch aper. Get yours today. aoe write ‘Bend me a Baby Calculator’’ and ive your name and address. We wi | it immediately, all charges_prepaid. de- livery pay postman $2 50. is is the lowest ed practical 4 ° der today. BABY CALCULATOR SALES CO, P.O. Box 1118, Dept. 2. Chicazo. |} Cateu- | m

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More Adventures of BURGESS RADIO BATTERIES The same Burgess Radio ‘A’, ‘B’ and ‘C’ Batteries which are today faith- fully serving the nation’s armed forces on land and sea and in the air, and used by leading radio broadcasting stations, experienced radio engineers and amateurs, are sold in your own community by your own dealer for your own receiving set. When you replace your old batteries, ask your dealer for Burgess. Insist upon this brand of laboratory prod- ucts—you will receive the same meas- ure of satisfactoryservice that haswon the confidence of the radio public. “‘Ask Any Radio Engineer’’ BURGESS BATTERY COMPANY Engineers DRY BATTERIES Manufacturers Flashlight - Radio - Ignition - ‘Yelephone General Sales Office: Harris Trust Bldg. Chicago Laboratories and Works: Madison, Wig. In Canada: —=_+ Niagara Falls and ||1!!"||| Buncess:! Sa _- (Caras

POPULAR SCIENCE MONTHLY April, 1925

A Radio-Frequency Amplifier (Continued from page 149) placed farther away from the secondary and tuned either by means of taps or a separate variable condenser. The secondary circuit consists of a coil connected with the grid and filament of the detector tube and tuned by means of a variable condenser or a variometer. The third circuit is a coil connected between the plate terminal of the detector tube and the plus-B binding post of the set. In some receivers this coil is ar-

4 - oor V/ kK ee i, nm) Soe ye “ey BINDING Post == BINDING POST Fig. 8—How to hook the radio-frequency amplifier to a regenerative receiver using primary can be used as coil X. The an- tenna binding post should be connected with binding post 6 of the radio- frequency amplifier instead of antenna ranged so that it can be rotated close to the secondary coil. This is known as tickler feed-back. In other sets a variom- eter is used to obtain feed-back by tuning the plate circuit. So-called single-circuit sets are those in which the secondary coil is also used as the primary. In order to hook up this radio-frequency- amplifier unit to your present receiver, you must first convert your set into a simple detector circuit and then place coil X, shown above dotted lines in Fig. 2, close to the secondary circuit of your receiver. How to do this is shown in Figs. 7, 8, and 9. The foregoing discus- sion of the principles on which the regen- erative ‘receiver operates is included only so that you may be able to figure out how to make the hook-up if your receiver is outwardly somewhat different from the ordinary types. +e IS assumed that your receiver already includes one or two stages of audio- frequency amplification, for most radio fans will not be interested in adding radio- frequency amplification unless they al- ready have a stage or two of awilio amplification to bring the signals they receive up to loudspeaker strength. Figure 7 shows the changes to be made in a so-called single-circuit receiver in order to add the radio-frequency ampli- fier. The coil X of Fig. 2 is here shown wound around the detector tuning coil after the antenna and ground have been removed and the tickler coil (the rotating coil) has been removed from the circuit. Be sure to take the tickler coil completely out of the circuit, for if you simply con- nect a wire across its terminals, you will

Fig. 9—How to hook the amplifier to a regenera- tive receiver using variocoupler and two variom- aperiodic primary. Four turns of the eters. that you can get down to four turns in the primary, connect asin Fig. 8; otherwise wind coil X on top of the old primary winding, which should be disconnected entirely from the new circuit have a choke that will kill the signal strength. Coil X should consist of about fou turns of wire. Any size will do—bel] wire is particularly recommended because the insulation is heavy enough to allow the wire to be wound on the tuning coil with. out fear of short circuits. One end of coil X is connected with the binding post that was formerly used for connecting the antenna, and this binding ——-——_—— —.

If your variocoupler has enough taps so post then should be connected with binding post No. 6 in the radio-frequency- amplifier unit. The other end of coil X should be connected with the plus-B amplifier binding post in your set. alert 8 shows how to combine the radio-frequency amplifier with an aperiodic regenerative tuner such, for in- stance, as was shown in the four-tube receiver described in the February issue. Here, the primary coil of the tuner will do very well as coil X, although it will be well to cut out all but four turns. The other changes consist in connecting the antenna binding post with binding post 6 of the radio-frequency amplifier instead of with the antenna, and then removing the other end of the coil from the ground binding post to the plus-B amplifier binding post in your receiver. Also cut the tickler coil out of the circuit. Figure 9 indicates the method of con- necting the radio-frequency amplifier with a regenerative receiver made up of a vario- coupler and two variometers. First dis- connect the stationary coil of the vario- coupler as shown in Fig. 9, and wind five turns of bell wire on top of the old winding and connect as shown. Then cut the plate variometer out of the circuit entirely. | After the tubes have been placed in the radio-frequency-amplifier unit and the rheostats G and H turned on so that the tubes are burning about as brightly as in the audio stages of your set, all the tuning can be done with the two dials on the radio-frequency-amplifier unit and the one dial of your present set. If you find that the signals are broken up by howls and squeals at just the point where they come

in strongest, turn potentiometer J slowly,

© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25.

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il, 1925 ignal four 2 the ’ the vith- 1 the 1 for ding 1VUVVV I 3 OB. OF + with ncy- il X us-B » the an r in- tube ssue. ill do well ther enna ’ the with ther ding post > coil con- with ario- ario- five ding olate 1 the the ; the as in ning the » one that and ome wly,

April, 1925

ajternating Light Current as B-Battery Substitute (Continued from page 76) can be made of drinking glasses with the plates hung over the sides. This is a poor method, however, as the water evapor- ates rapidly and a crust will form all over the tops of the glasses. er The level of the borax solution in the jars or glasses should be adjusted so that the aluminum plates will have not more than one square inch exposed to the solution. After you have constructed the rec- tifier, connect it with the current supply, as shown in Fig. 2, with a 50- to 100-watt lamp inthe socket. Be sure to connect thelead and aluminum plates exactly as shown. If everything is right, the lamp will light almost to full brilliancy and then gradually become dimmer and finally go out altogether. If the lamp does not go out, it is a sign that something is wrong. If you are sure that there are no short circuits in the construction of the caps, try reducing the level of the solution in the jars. If this has no appreciable effect, the chances are that the aluminum is not sufficiently pure for rectifier use. After the rectifier is working properly as indicated by the lamp’s going out, refer to the table at the bottom of page 76 and note the capacity values of the condensers to be used at C,, C., and C,, according to the number of tubes in your radio set. The primary circuit of an alternating- current bell-ringing transformer can be used for the inductance L. Such trans- formers are obtainable in any electrical supply store at a cost of not more than two dollars. Most of the larger stores carry telephone condensers of one- or two- microfarad capacity, suitable for use in this circuit. A variable resistance of the graphite disk type will do very well at R. Practically all of the receiving sets made today have the secondary and fila- ment circuits grounded, and since the minus-B-battery terminal is always con- nected with the filament circuit inside the radio receiver, it will be necessary to place a condenser in series with the ground lead of the receiver. Otherwise the electric-light current will be grounded and the fuses will blow. The value of this insulating condenser is unimportant so long as it is above .002 microfarad. The half-microfarad by-pass condensers are satisfactory for use at this point in the circuit. The simplest arrangement of the B- battery eliminator is to place the rectifier jars in any convenient corner and mount the parts of the filter circuit on a piece of board fastened to the wall just above the rectifier jars. Do not inclose the jars, for they have a tendency to heat up after several hours of operation, and if they are closed in the temperature of the solution will rise to a point where the jars no longer will act as rectifiers. For this reason it is well also to place a double- Pole, single-throw switch in the supply line so that the rectifier can be cut off from the house current when the radio set 8 not in use. If the vent hole is small, the rectifier should give from six to eight

months’ service without attention. 0

© This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. POPULAR SCIENCE MONTHLY 151 5 Sensitivity With the extreme acuteness of the bloodhound’s scent, the Model L-2 Ultradyne detects the faint- est broadcast signals—signals that ave “dead” to other receivers—regenerates and makes them audible on the loud speaker.

You (an Build the GLTRADYNE MODEL L-2 . With this Book _ UILD this famous receiver yourself and save money. This book,*“‘How to Build and: Operate Ultradyne Model L-2,” by R. E. Lacault, E. E., A. M. I. R. E., originator of the Ultradyne, makes it easy for anyone to build this remarkable receiver. The Ultradyne book explains the ““Modulation System” of radio reception and a special adaption of regener- tion, as used exclusively in the Model L-2 Ultradyne. This is the latest development of R. E. Lacault, Chief Engineer of this Company and formerly Radio Re- search Engineer with the French Signal Corps Research Laboratories. This exclusive feature makes the Ultradyne the most sensitive set known—capable of detecting the faintest broadcast signals, making them audible on the loud speaker. Also the most selective receiver known—regardless of close similarity in wavelength, the Ultradyne selects any station within range, brings in greater distance, clearly, distinctly, faithfully, on the loud speaker. The regular advertised price of the Ultra- dyne book is 50c. This 25c Coupon is a special offer only to introduce the Ultradyne Circuit to readers of Popular Science.

= SODOPOE| Co os “< LNODYOSODOSSA SSeS = ay Ss SIN INA=SNA, \SARASARAGASAGIEKEEIG? ‘ ¢

PHENIX RADIO CORPORATION, 5-7-9 BEEKMAN ST., NEW YORK CITY Gentlemen: Enclosed find 25c in stamps, together with coupon valued at 25c, for which please send me your regu- larly priced Book of Instructions on ‘‘How to Build and Operate Ultradyne Model L-2.” Standard Price 50c | VEVAVAVAVAY AV EVEVEVEVE ae "| A A CSOD OSS SSSI = = f= = co

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POPULAR SCIENCE MONTHLY The brass stator plates are soldered to notched spacer bars that main- tain perfect alignment. Brass Plates Low Loss Low Minimum er” ~~. and distinctive features are embodied in the design of the Bradleydenser. For instance, the rotor revolves Plates, spacer bars and end plates a i e are all soldered into a solid unit. on a long double bearing that preserves rigid alignment and yet eliminates the extra outer end-plate. ‘This reduces the amount of di-electric material and increases the efficiency. Saye HERES RL LEI NE, I ee he aay We aN so Every joint is soldered. This, combined with the use of brass plates, further increases the operating efficiency. Another feature is the dust cap over the stator plates; it is removable without tools. The Bradleydenser is made in four sizes: 0.00025 M-f. at = $4.50; 0.00035 M-f. at $4.75; 0.0005 M-f. at $5.00; and 0.001 The bearing stud, attached to the M-f. at $6.00. Leading radio dealers are showing them, now. stator mounting plate, supports the rotor. See illustration at bot- tom of this page. Allen Bradley Ca. Electric Controlling Apparatus 293 Greenfield Avenue MILWAUKEE, WIS. Manufacturers of Electric Controlling Apparatus for Over Twenty Years Fee Serer Rotor revolves on a double bear- ing that is independent of the dial shafr. Disassembled view of the Brad- leydenser showing bearing construction, rotor assemblyand 2 detachable dial shaft. The shaft does not carry’the weight of - the rotor. © This seal on a radio or tool advertisement signifies the approval of the INSTITUTE OF STANDARDS. See page 25. ART COLOR PRINTING cO., NEW YORK